we sometimes use be able to instead of can and could to talk about ability.however,we avoid be able to:l

when we talk about something that is happening as we speak:l*

example:whatch me mum,I can stand on my leg(not....I'm able to stand on my leg)l

before passives:l*

example:CDs can now be copied easily.(rather than CDs are now able to be copied...)l

when the meaning is 'know how to'l

example:can you cook?(rather than are you able to cook?)l

if we talk about a single achievement , rather than a general ability in the past ,we usually use be able to rather than could.compare:l

example:sue could play the flute quite well.(or ...was able to ....;a general ability)and

sue swam strongly and was able to cross the river easily ,even though it was swollen by the heavy rain.(not she swam strongly and could cross ....;a specific achievement)l

 however ,could is usually more natural

in negative sentences:l*

I tried to get up but I couldn't move.(rather than ....I wasn't able to remember...)l

with verbs of sence-e.g.feel,hear,see,smell,taste-and with verbs of 'thinking'-e.g. believe,decide,remember,understand:l*

I could remember the crash ,but nothing after that.(rather than I was able to remember....)l

after the phrases the only thing/place/time,and after all when it means 'the only thing'*

All we could see were his feet.(rather than all we were able to...)l

to suggest that something almost didn't happen,particularly with almost,hardly,just,nearly:l

I could nearly touch the ceiling(rather than I was nearly able to...)l*

can and could:talk bout possibility

to talk about the theoretical possibility of something happening we use could ,not can.however,we use can,not could,to say that something is possible and actually happens.compare:l

example:It could be expensive to keep a cat.(=if we had one,it could or it may not be expensive)and

It can be a expensive to keep a cat .(=it can be,and it sometimes is)l

we use can't,not couldn't,to say that something is theoretically or actually impossible:l

example:there can't be many people in the world who haven't watched television.l

the doctor can't see you this morning;he's busy at the hospital

we use can to indicate that there is  a very real possibility of a future event happening.using could suggests that something is less likely or that there is some doubt about it.compare:l

example:we can stay with Jim in Oslo.(=we will be able to stay)and

we could stay with Jim in Oslo.(=it's possible ;if he's there)l

could and be allowed to:talking about permission

to say that in past someone had general permission to do something - that is,to do it at any time - we can use either could  or was/were allowed to.however,to talk about permission for one particular past action,we use was/were allowed to ,but not could .compare:l

example:Anyone was allowed to fish in the lake when the council owned it.(or....could fish.....)and

Although he didn't have a ticket,Ken was allowed to come in.(not...could come in.)l

In negative sentences,we can use either couldn't or wasn't/weren't allowed to ,to say that permission was not given in general or particular situation:l

example:We couldn't/weren't allowed to open the presents until Christmas mirning

نظرات شما عزیزان:

نام :

آدرس ایمیل:

وب سایت/بلاگ :

متن پیام:

نظر خصوصی

 کد را وارد نمایید:

 

 

 

عکس شما

آپلود عکس دلخواه: