问题
选择题
To protect the environment, the local government has put up a lot of ______ to warn the citizens not to litter the ground.
A．sighs
B．sights
C．signals
D．signs
答案
答案：D
题目分析：A. sighs叹息，B. sights 视野，景色，C. signals信号，D. signs标志，迹象，句意：为了保护环境，当地的政府竖立很多标志警告市民不要乱扔垃圾。根据句意选D。