第13题: [单项选择]This book ______ me twenty dollars. A. is cost B. was cost C. cost D. have been cost 参考答案:C 答案解析:[注释] 英语中某些表示状态或特征的动词,如become,lack,contain,fit,have,cost, suit,resemble等没有被动语态。
第16题: [单项选择]What is the main topic of this passage A. Use of sea water. B. Treatment of sea water. C. Chemical properties of magnesium. D. Derivation and users of magnesium. 参考答案:D