He found it hard for Alan to focus on his teachers for longer than five minutes, _________ if the lecture was boring.
Your ability has never been in doubt-- the question is ____ you are prepared to work hard.
At last we came to a mountain, at the top of which ______,
---Must I take this medicine, Mom? It ________ so terrible. ---Yes, you must take it for another three days.
The audience are _______young people who like pop music at the concert.
--- What does the model plane look like? ---Well, the length of its wings is _______ of its body.