单层厂房常用柱截面形式一般可参照柱截面高度h来选型，当h=1300～1500mm时，应选用下列中哪种截面（）？

A.矩形或工字形截面

B.工字形截面

C.工字形或双肢柱

D.双肢柱

—Do you know the girl _____ is playing the guitar?

—Yes, she is Jack's sister.[ ]

A. whom

B. which

C. who

D. what