1．Some biologists believe this is an ancient survival strategy, _______ a diet with 30 percent
fewer calories than usual increased life span.
A. for which B. to which C. of which D. in which
2．Make sure that your speech is _________ and to the point, so that the audience will not get bored just because they have to listen to you talking for a long time.
A. brief B. attractive C. humourous D. powerful
