第二部分:单项选择(共20小题;每小题1分,满分20分)
21.Last week I bought several reference books for my English study, including handbook of grammar and second-hand book on how to memorize vocabulary.
A.the; the B.a; a C.a; the D.the; a
22.Too much to X-rays can cause skin burns, cancer or other damage to the body.
A.connection B.approach C.contact D.exposure