第21题: [单项选择]The last half of the nineteenth century ______ the steady improvement in the means of travel. A. has witnessed B. was witnessed C. witnessed D. is witnessed 参考答案:C 答案解析:[解析] 根据主语可判断出时间为过去时。
第31题: [填空题]What if a child has poor chemistry with the teacher 参考答案:We should increase their time of being together to improve their relationship. 答案解析:[题解] 考查对文章"Poor Chemistry With a Teacher" 部分句子"Having the teacher and child sit down for lunch toget