请认真阅读下面各题，从题中所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑。
21. Failure to face up to painful experience can be ______ form of stress itself, and can increase ______ possibility of illness.
A. the; / B. a; a C. a; the D. /; the
22. It is widely accepted that parents should raise their children more by ______ than by anything else.
A. contrast B. force C. example D. nature
23. Many college graduates are willing to start online shops to get over the period ______ they have difficulty finding a satisfactory job.
A. where B. when C. which D. that
24. While taking notes, she often uses colored pens for different topics to catch the eye and make things ______.
A. stand out B. give out C. drop out D. go out
25. As a writer, I like ______ when people send me pictures of their lovely children reading my books.
