第35题: [单项选择]It was essential that the application forms ______ back before the deadline. A. must be sent B. would be sent C. be sent D. were sent 参考答案:C 答案解析:[解析] 在表示“必须、重要、希望”等的形容词advisable,compulsory,crucial,desirable,essential,imperative,important,(im)pro