Every year people go to visit their factoryA. a thousand of B. thousandsC. thousand ofD.

问题补充：

Every year, people go to visit their factory

A. a thousand of

B. thousands

C. thousand of

D. thousands of

答案：

A. a thousand of

B. thousands

C. thousand of

(答案→)D. thousands of

解析：句意：每一年都有成千上万的人们去参观他们的工厂。thousands of成千上万，不确定的所指，故选D