哺乳动物的运动系统包括：

A．骨骼肌、关节

B．骨、关节、肌肉

C．骨、关节、神经

D．骨骼肌、关节、神经

In the past few years there ______ great changes in my hometown. [ ]

A. have been

B. were

C. had been

D. are