Are Kate and Joan ______ good friends –Yes， they are. Please look after ______.

Someone who lacks staying power and perseverance is unlikely to ________a good researcher.

it’s a challenging job, he did itittook me．

tired professor, _____ in his new book in thepast three years, hasn’t realized the decline in his health

The old lady died from the _____on her head; she was _______when cleaning windows on the ladder when she fell off it.