I think you should complain —___________,of course, you are happy with the way things are.

A．if

B．unless

C．as

D．because

喷气纺纱的加捻是由假捻转化为（）的过程，这种真捻与环锭纱的真捻具有本质的区别。

A.间隔真捻

B.连续真捻

C.包芯真捻

D.包缠真捻