Употребите MAY, MIGHT, CAN, COULD по смыслу
a) He said that he.....ship the goods in September.
b) If you had tried harder you....have succeeded.
c) It is strange John isnt`t here. He.....have forgotten about our appointment, or he.....have come white I was out.
d).....he have refused to help you?
e) I said that he......not have missed the train, as he had left the house very early.