Unit 1 Festivals around the world

you could have told us earlier.
tom could have taken the dictionary.
4. ought to / should have done和 ought not to / shouldn’t have done
ought to / should have done 和 ought not to / shouldn’t have done 用于對已發生的情況表示“責備”、“不滿”，分別表示“本應該…”和“本不應該…”。例如：
1）with all the work finished, i should have gone to the party last night.
2）you ought not to have made fun of him. he is not the one you laugh at but learn from.
5. needn’t have done
needn’t have done 表示過去做了某事，但沒有做的必要， 意為“本沒必要…”。
you needn’t have waken me up; i don’t have to go to work today.
注：表示推測過去某動作發生的可能性時，就表示的可能性程度而言，must最大，could其次，may更次之，might最小。例如：
“i wonder how tom knew about your past.”
“he must / could / may / might have heard of it from mary.”
二、情態動詞+動詞進行式
情態動詞+行為動詞進行式（即情態動詞+ be + doing形式），表示推測或評論某動作現在是否正在進行。例如：
1）he must be playing basketball in the room.
2）she may be staying at home.
三、情態動詞+動詞完成進行式
情態動詞+行為動詞完成進行式（即情態動詞+ have been + v-ing 形式），表示推測或評論過去某動作是否正在進行或一直在進行。例如：
1）they should have been meeting to discuss the problem.
2）he may / might have been buying stamps in the post office when you saw him.
四、某些情態動詞的特殊用法
1. need
考試中主要測試 need 作情態動詞與作實義動詞的區別.
情態動詞need與實義動詞need 在時態、肯定、否定結構上的對比見下表。
時態 情態動詞need 實義動詞 need
現在時 he need (needn’t) do
need he do….? he needs (doesn’t need) to do
過去時 he needed (didn’t need) to do
將來時 he need (needn’t) do
need he do….? he will (not) need to do
注: need 一般用于否定句或疑問句.
2. dare
考試中主要測試dare作情態動詞和作實義動詞的區別。
情態動詞dare 與實義動詞dare 在時態、肯定、否定、疑問結構上的對比見下表。
句型 情態動詞dare 實義動詞 dare
肯定句 現在時 dare to 少用
過去時 dare to 少用 現在時 dare/dares to do
過去時 dared to do
否定句 現在時 daren’t/dare not do
過去時 dared not do 現在時 do/does not dare (to) do
過去時 did not dare (to) do
疑問句 現在時 dare he do?
過去時 dared he do? 現在時 do you/does he dear (to) do?
過去時 did he dare (to) do
3. can 和 may
考試中主要測試can，may或could，might表示可能性的區別及對may構成的疑問句的回答。
（1）can, could, may, might都可以表示可能性.can, could表示潛在的可能性或理論上或邏輯判斷上存在的可能性；而may, might則表示事實上的可能性。此外，can還具有“有能力”的意思，而may與might則不具此意。例如：
according to the weather forecast, it may rain tomorrow.