精选优质文档-倾情为你奉上英语专业四级2003-2013年单选选择题真题及答案2003年51. Agriculture is the countrys chief source of wealth, wheat _ by far the biggest cereal crop.A. is B. been C. be D. being答案：D 参考译文：农业是这个国家财富主要的来源，其中小麦是最主要的谷类作物。 【试题分析】 本题考查对非谓语动词的掌握。 【详细解答】 这是一个独立主格结构。wheat前用逗号，且没有连词，表示这一句起补充说明的作用，该空不能用动词的形式，则being为唯一之选。52. Jack _from home for two days now, and I am beginning to worry about his safety.A. has been missing B. has been missed?C. had been missing D. was missed答案：A 参考译文：到目前为止，
