1.Such________the case, I couldn't help but ________ him.
A.being；support B.is；to support
C.has been；supporting D.be；supported
解析： can't help but为固定短语， but后面接不带to的不定式；Such being the case为独立主格结构，the case为逻辑主语。
2. The article _________ on this subject was written by Mr.Black.A. referring B. referred C. referring to D. referred to
3. In order not to be disturbed, I spent three hours ________in my study.A.locking B.locked C.to lock D.being locked
解析： lock与其逻辑主语应含有动宾关系，即 "被锁在书房里"。
4. Will you lend him a magazine _________A. to be read B. for reading C. to read D. he read
解析： 不定式作定语,to read 的逻辑主语是间接宾语him.
5. The little boy still needs the _____ (remain ) 20 dollars to do with some things _____(remain; settle).（填空练习）
答案：remaining; remaining to be settled
解析： 第一个remaining用作形容词，作“剩下的”解；第二个remaining to be settled 是-ing形式短语作定语。
6.Mr. Smith was much surprised to find the watch he had had _____(repair) was nowhere to be seen.（填空练习）
解析： he had had repaired是省去了关系代词that/ which的定语从句。
1、疑问词 + 动词不定式：疑问代词和疑问副词后可加动词不定式构成不定式短语，在句中可作主语、表语或宾语，如：How to prevent them from swimming in this river is a problem.
2、动词不定式的否定式：动词不定式的否定式是由not + 动词不定式构成，如：It’s wrong of you not to attend the meeting.