6. Fill the spaces in the following sentences by using one of these forms + the perfect infinitive of the verbs in brackets.
must + perfect infinitive is used for affirmative deductions can't/couldn't + infinitive is used for negative deductions. needn't + perfect infinitive is used for a past action which Was unnecessary but was performed.

31. I had to get down the mountain in a thick fog. ~ That ... (be) very difficult.
32. I saw Ann in the library yesterday. ~ You ... (see) her; she is still abroad.
33. How did he get out of the house? He ... (come) down the stairs for they were blazing.
34. You ... (lend) him your map. He has one of his own.
35. I spoke in English, very slowly. ~ You ... (speak) slowly. He speaks English very fluently.
36. He was found unconscious at the foot of the cliff. He ... (fall) 200 metres.

That must have been coldn't have seencould't have comeneedn't have lentneedn't have spokenmust have fallen