第一节 单项填空(每小题1分,共15小题15分)
21. Pets need a lot of care and __________; you can not leave them alone for a long time.
A. patience B. attention C. courage D. responsibility
22. He invented a lot of things, many of taken granted by people.
A. them; for B. which; for C. what; of D. which; of
23. Buying a train ticket ahead of time will usually ______ you a good seat.
A. arrange B. guarantee C. protect D. prevent