B. We use the modal 'can' to make general statements about what is possible or allowed, or that somebody has the ability to do something: can + infinitive (can do/ can see etc.) (e.g. It can be very cold in winter. (= It is sometimes very cold in winter))
a. use 'could' as the past tense of 'can' (e.g. Listen. I can hear something. (now), I listened. I could hear something. (past)), we also use 'could' especially with: see, hear, small, taste, feel, remember, understand. (e.g. We had a lovely room in the hotel. We could see the lake.)
b. use 'could' to show that something is possible in the future, but not certain. (e.g. If we don’t hurry we could be late. (=Perhaps/Maybe we will be late))
c. also use 'could' to talk about possible actions now or in the future (especially to make suggestions) (e.g. A: What shall we do this evening? B: We could go to the cinema.) 'Can' is also possible in these sentences (e.g. We can go to the cinema. etc.) With 'could', the suggestion is less sure.
d. use 'could have' to show that something 'is/was' possible now or at some time in the past. (e.g. It’s ten o’clock. They could have arrived now.)
e. We use the negative 'can’t' or 'cannot' to show that something is impossible. (e.g. That can’t be true. You cannot be serious). We use 'couldn’t/could not' to talk about the past. (e.g. We knew it could not be true.)
Idiom 365
Hit The Nail On The Head: to do or say exactly the right thing in the most effective and efficient way.
Example: He hit the nail on the head when he said the problem was the mis-communication.