زبان ویدیو: در این ویدیو قسمت هشتم از سری دوم مجموعه آموزشی Study English برای آمادگی آزمون آیلتس را با زیرنویس انگلیسی و متن ترانسکریپت کامل ویدیو برای شما آماده شده است.
متن ترانسکریپت ویدیو
Hello. I’m Margot Politis. Welcome to Study
English, IELTS preparation.
Today we’re taking a look at tenses. We’ll
focus on the present perfect and simple past
tenses, and we’ll hear examples of each.
Then, we’ll practice using some adverbs of time.
The clip we’re looking at today is about greenhouse
gases. Scientists have been measuring the
concentration of certain gases, stored in
ice in Antarctica. Let’s find out more.
The air archived in ice helps prove how much
the level of greenhouse gases in the atmosphere
has changed in just the last two hundred years.
What we’ve found out is that indeed there
were much lower concentrations pre-industrially,
around about a third of the methane concentration
that we have presently. We’ve seen a big increase
in carbon dioxide, so the two main greenhouse
gases in the atmosphere have increased.
If you look back a half a million years ago,
we don’t see concentrations anything like
we have presently. We can link those high
concentrations of the present day uniquely
to activities of man – combusting of fossil
fuels, clearing of lands and so on, agricultural activities.
As you know, there is a variety of verb tenses
in English – simple, perfect and continuous.
Tenses are used to describe ‘past’, ‘present’ and ‘future’ actions.
Sometimes, we need to give more information
about when an action happened, how long it
happened for and whether it is continuing.
When an action has been completed, we use
the present perfect tense.
Listen to Dr Etheridge use it here.
What we’ve found out is that indeed there
were much lower concentrations pre-industrially,
around about a third of the methane concentration
that we have presently. We’ve seen a big increase
in carbon dioxide, so the two main greenhouse
gases in the atmosphere have increased.
Dr Etheridge uses the present perfect tense.
He says: ‘we’ve found out’
He’s talking about an action that has been completed.
He also says: ‘we’ve seen’, and ‘greenhouse gases have increased’.
These actions started sometime in the past
but have now been completed – they are in
the present perfect tense.
When an action has only recently been completed,
we can highlight this by using the adverb
‘just’.
Listen to the reporter.
The air archived in ice helps prove how much
the level of greenhouse gases in the atmosphere
has changed in just the last two hundred years.
She says that: “The level of greenhouse gases
has changed in ‘just’ the last two hundred years”.
By using the word ‘just’, she is telling us
that two hundred years isn’t very long in
geological time. It’s only ‘just’ happened.
She’s also using the present perfect tense.
Let’s have a look at how we structure the
present perfect tense.
We use the auxiliary verb ‘to have’ and a
past participle.
So here’s our auxiliary verb:
to have – I have, you have, she has, we have,
they have And then a past participle – for example:
changed, found out, seen, increased or helped.
So we have:
I have changed you have found out
she has seen we have increased
they have helped
Now let’s take a look at the simple past tense.
We use the simple past tense when an action
occurs at a particular time in the past.
For example:
last Christmas or on the 15th of May or in 1979, or three million years ago.
Let’s listen to Dr Etheridge.
What we’ve found out is that indeed there
were much lower concentrations pre-industrially,
around about a third of the methane concentration
that we have presently.
He says that: “There were much lower concentrations
pre-industrially.”
This refers to a particular time in the past
– that is, ‘pre-industrially’ or ‘before the
industrial revolution’ in Europe.
The atmosphere was cleaner then because there
weren’t industries producing greenhouse gases
and other pollution.
So, the simple past tense describes an action
that occurred at ‘a specific time’ in the past.
But the present perfect tense describes an
action that has been completed at ‘some indefinite
time’ in the past.
We’ve already seen how the reporter uses the
adverb ‘just’. ‘Just’ is an adverb of time.
There are several adverbs of time. They can
be used with the present perfect tense to
give a number of different meanings.
Listen again.
The air archived in ice helps prove how much
the level of greenhouse gases in the atmosphere
has changed in just the last two hundred years.
The reporter uses the adverb ‘just’.
When you are using the present perfect to
talk about a recently completed action, you
can use the adverbs ‘just’, ‘already’, ‘yet’ or ‘still’.
For example:
The level has changed in ‘just’ two hundred years.
The Earth’s atmosphere has ‘already’ been destroyed.
The adverbs of time ‘yet’ and ‘still’ are
used in question forms and negative constructions.
For example:
Have you finished your assignment yet?
No. I am still writing the introduction.
Or: Have you finished your assignment yet?
No I haven’t written the introduction yet.
When we’re using the present perfect tense
to talk about an action that took place at
some ‘indefinite time’ in the past, we can
use the adverbs of time ‘ever’ and ‘never’.
‘Ever’ is often used in questions. It means
‘has the thing been done at any time in the past’.
Some examples are:
Have you ever been to China?
No, I’ve never been there.
Finally, when we’re talking about an action
that took place at a point in the past, up
to and including now, we can use the adverbs
of time ‘for’ ‘from’ and ‘since’.
For example:
I have been at this school for three months,
since March.
So you can see that there are different adverbs
of time for different uses of the present perfect.
The present perfect is a difficult tense to learn.
It’s used in statements about actions that
began in the past and are still true now.
But it can take a lot of practice to get right.
Using adverbs of time can be useful because
they help to clarify the precise use of the tense.
Practice using adverbs of time, and you’ll
find making the right choice becomes much easier.
And that’s all for Study English today.
Let’s review what we’ve done.
We’ve looked at the simple past tense, and
the present perfect tense.
And then we talked about using adverbs of
time in these present perfect constructions.
Don’t forget that you’ll find more on these
topics on our website.
دانلود ویدیو و زیرنویس انگلیسی
لینک دانلود ویدیو: دانلود مستقیم
دانلود زیرنویس
[/ihc-hide-content]
