问题
选择题
—What is behind the tree?
—There must be a dog ______ there. [ ]
A. to sit
B. sit
C. sitting
答案
答案：C
搜题请搜索小程序“爱下问搜题”
—What is behind the tree?
—There must be a dog ______ there. [ ]
A. to sit
B. sit
C. sitting
答案：C