问题
选择题
Some little boys have difficulty ______their hearts into the lesson for a long time.
A．to put
B．to put
C．putting
D．puting
答案
答案：C
此题考查固定句型结构have difficulty in doing sth表示做某事有困难，其中in可以省略。动词put的现在分词形式putting。故选C。