[例1]—— Did that book give the information you needed？
—— Yes，but______，we had to read it almost entirely.
A.for finding it B.to find it
C.finding it D.by finding it
【解析】答案B。不定式“to find it”作目的状语，“为了找到需要的信息，我们不得不把整本书读一遍”。
[例2]Charles Babbage is generally considered______the first computer.
A.to invent B.inventing
C.to have invented D.having invented
【解析】答案C。“通常人们认为是Charles Babbage发明了第一台计算机”，不定式“to have invited”作主语补足语。
[例3]There isn’t any difference between the two.I really don’t know____.
A.where to choose B.which to choose
C.to choose what D.to choose which
【解析】答案B。“这两者没有什么区别，我真的不知道选择哪一个”，不定式to choose作know的宾语。
[例4]What the scientist said greatly encouraged us______the experiment again，but his secretary’s words discouraged us______the experiment any more.
A.to try；to do B.to try；from doing
C.for trying；from doing D.trying；to do
【解析】答案B。“鼓励某人做某事”，用encourage sb to do sth.所以，第一个空填to try；相反，“不鼓励某人做某事”，用discourage sb from doing sth。
[例5]She felt it a great shame______so severely in the presence of her boy friend.
A.to criticize B.to have criticized
C.to be criticized D.to have been criticized
【解析】答案D。“她感觉在男朋友面前遭受如此严厉的批评真是一种耻辱”，不定式完成被动形式“to have been criticized”在此作宾语补足语。
[例6]John was made______the truck for a week as a punishment.
A.to wash B.washing C.wash D.to be washing
【解析】答案A。“他被惩罚洗卡车一周”，“to wash”作主语补足语，原本是“make sb do sth”句型，在这用被动语态，不定式需要加不定式符号“to”。