He found it hard for Alan to focus on his teachers for longer than five minutes, _________ if the lecture was boring. 

Compared with male graduates，a(n)______small number of female graduates can get employed when they go job-hunting.

His report was so exciting that it was      interrupted by applause(鼓掌).

    Dream of the Red Chamber is ________worth ________because we can learn a    lot about the noble families in the feudal society.

You’d better book the tickets in advance; _______ we may miss the concert.