21. Of all the subjects, I like ____ history best because it gives us ____ useful knowledge of things in the past.
A. the; a B. 不填; a C. a; the D. a; 不填
22. He lost his job three years ago; _____, he was seriously injured in an accident last week.
A. in the first place B. worse still C. on the contrary D. in other words
23. ---I failed today’s math test! What shall I do?
---____! Try once more.
A.Come on B. Hurry up C. Take it easy D. Don’t mention it
