3 edited title
| link

can 'can/couldcould' and bee'be able toto'

2 I made the format a little prettier.
source | link

I have two questions about exercises of English grammar in use. In this exercise I need to feel the blank with can if possible or be able to otherwise. Correct answer in brackets:

26.1.4 I used to (be able) stand on my head, but I can't do it now

26.1.4 I used to (be able) stand on my head, but I can't do it now

I didn't get why 'could' isn't correct. It just sounds incorrect to use 'could'. I want to understand rule behind it. Standing on head sounds like general ability and 'can' should be used then we speak about general ability. Why 'could' isn't suitable for this sentence?

26.1.5 I can't understand Martin. I've never (been able to) understand him.

26.1.5 I can't understand Martin. I've never (been able to) understand him.

I feel like ability to understand person is general. I didn't get why 'could' is incorrect here.

I have two questions about exercises of English grammar in use. In this exercise I need to feel the blank with can if possible or be able to otherwise. Correct answer in brackets

26.1.4 I used to (be able) stand on my head, but I can't do it now

I didn't get why 'could' isn't correct. It just sounds incorrect to use 'could'. I want to understand rule behind it. Standing on head sounds like general ability and 'can' should be used then we speak about general ability. Why 'could' isn't suitable for this sentence?

26.1.5 I can't understand Martin. I've never (been able to) understand him.

I feel like ability to understand person is general. I didn't get why 'could' is incorrect here.

I have two questions about exercises of English grammar in use. In this exercise I need to feel the blank with can if possible or be able to otherwise. Correct answer in brackets:

26.1.4 I used to (be able) stand on my head, but I can't do it now

I didn't get why 'could' isn't correct. It just sounds incorrect to use 'could'. I want to understand rule behind it. Standing on head sounds like general ability and 'can' should be used then we speak about general ability. Why 'could' isn't suitable for this sentence?

26.1.5 I can't understand Martin. I've never (been able to) understand him.

I feel like ability to understand person is general. I didn't get why 'could' is incorrect here.

1
source | link

can/could and bee able to

I have two questions about exercises of English grammar in use. In this exercise I need to feel the blank with can if possible or be able to otherwise. Correct answer in brackets

26.1.4 I used to (be able) stand on my head, but I can't do it now

I didn't get why 'could' isn't correct. It just sounds incorrect to use 'could'. I want to understand rule behind it. Standing on head sounds like general ability and 'can' should be used then we speak about general ability. Why 'could' isn't suitable for this sentence?

26.1.5 I can't understand Martin. I've never (been able to) understand him.

I feel like ability to understand person is general. I didn't get why 'could' is incorrect here.