21. _____ English language is _____ useful tool,
A. An; a Ｂ. /; an C. The ; a D. /; a
22. It was _____ the car that he spent 3 hours yesterday.
A. repaired B. repairing C. to repair D. in repair
23. Before you left your position, you should consider the effect _____ will have on you.
A. the one B. as C. which D. it
