问题详情：
![Sincethetimehumankindstartedgardening,we]( "Sincethetimehumankindstartedgardening,we")
Since the time humankind started gardening, we _____to make our environment more beautiful.
A. try B. have been trying
C. are trying D. will try
【回答】
B【解析】考查动词时态。根据since引导的时间状语从句可知所填词表示“从过去一直持续到现在的动作”，强调其持续*，应用现在完成进行时，故选B。
知识点：现在完成进行时及其被动式
题型：选择题
