21. She was scared _______ when hearing the sound of explosion.
A. to death B. death C. of death D. with death
22. -- We are going to hold a sports meeting tomorrow.-- __________ it rains?
A. How about B. What if C. If only D. Even if
23. Is _______ some German friends visited last week?
A. this school B. this the school C. this school one D. this school where
24. Students are encouraged to _________ the design competition for robots at the university.
A. take part B. operate C. join to D. participate in