A1. Possibility: We use the modals 'could', 'might' and 'may' to show that something is possible in the future (but not certain). (e.g. They might come later. (= Perhaps/Maybe they will come later.))
a. We use 'could have', 'might have' and 'may have' to show that something was possible now or at some time in the past. (e.g. It’s ten o’clock. They might have arrived now.)
b. use the modal 'can' to make general statements about what is possible. (e.g. It can be very cold in winter. (= It is sometimes very cold in winter))
c. use the modal 'could' as the past tense of 'can'. (e.g. It could be very cold in winter. (= Sometimes it was very cold in winter.))
d. Impossibility: 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.)
e. We use 'couldn’t/could not' to talk about the past. (e.g. We knew it could not be true. He was obviously joking. He could not be serious.)
Idiom 365
Get Over It: to get something better than happened in the past, and move on
Example: We need to get over it and focus on the next subject.