When changing lanes, a driver should use his turning signal to let other drivers know _____.[ ]

A. he is entering which lane

B. which lane he is entering

C. is he entering which lane

D. which lane is he entering

在质量管理领域，西格玛用来表示（）。

A.数据的离散程度

B.质量控制水平

C.质量管理有效性

D.产品效益水平