国际单位制中，下列计量单位名称、单位符号正确且属于基本单位的是（）。

A.坎，cd

B.伏特，V

C.热力学温度，K

D.瓦特，W

—Many tourists ________to the Great Wall every year.

—Yes, that’s true.

A．attract

B．have attracted

C．are attracting

D．are attracted