Things to say on special occasions or at special moments, asking for and giving an opinion, pausing to think, asking for permission, giving and refusing permission, expressing preferences, promising, reassuring, recommending, refusing to do something, making and responding to a request, suggesting, thanking | Explanations Ability Could and was able to To talk about general past ability we use could. When I was young I could run very fast. To talk about one specific past action we use was able to. Luckily Mary was able to help us. Certainty and uncertainty Must have and can t have These are used to make logical deductions about past actions. I must have left my wallet in the car. I am sure I did Jim can t have noticed you. I am sure he didn t May have might have and could have These express possibility or uncertainty about past actions. Jean might have missed the train. perhaps she did He may not have received the letter. perhaps he didn t You could have been killed it was a possibility Was Were to have This describes something which was supposed to happen but didn t. It is formal in use. He was to have left yesterday. he was supposed to leave but he didn t Obligation Had to Must has no past form so we use had to. Sorry I m late I had to take the children to school. The question form is Did you have to Did you have to work late yesterday - Should have and ought to have These express the feeling that a mistake was made. There is a criticism. I should have posted this letter yesterday. I didn t do the right thing You shouldn t have told me the answer. you were wrong to do so Needn t have and didn t need to There is a slight difference between these two forms. Compare needn t have arrived at seven. I arrived at seven but it wasn t necessary didn t need to arrive at seven. we don t know when I arrived - maybe seven or later But in everyday speech we often use didn t need to for both cases. 98 GRAMMAR 17 MODAL VERBS PAST Pronunciation and In speech have is often contracted in the forms in this unit. writing I must ve left my wallet in the car. Indirect speech Must and shall In indirect speech see Grammar 6 must is reported as must or had to. Shall is reported as should. You must go. He told me I must go. He told me I had to go. Shall I help He asked if he should help. 99 .
