—Where is my music disc? I can’t see it!

—You’d better________ the disk carefully in your bedroom.

A．look up

B．look for

C．look after

D．look through

（）是指能够影响其它变量，而又不受外界因素的影响而自身产生变化的变量.而（）是指不能影响其它变量，而又受外界因素影响而变化的变量.