71 A starting -> to start ( advise + SO + to V/ not to V )
72 A taught -> has taught ( for -> hiện tại hoàn thành )
73 B in the time -> by the time ( quá khứ hoàn thành + by the time + quá khứ đơn )
74 B see -> seeing ( look forward + to + Ving )
75 B is -> are