单选题 He left orders that no one ______ his study until he came back.
A. should enter B. ought to enter C. must enter D. would enter

【正确答案】 A

【答案解析】[解析] 动词虚拟式题。在decision，decree，demand，instruction，order，requirement等名词之后出现的同位语that从句中，动词要采用虚拟式。一种是be型虚拟式，另一种是“should+不定式”。比如，We were faced with the demand that this tax (should) be abolished. 我们面临取消这个税收的要求。