—Oh, I've just locked my keys in my office again.

—You're always so careless, but ________ let's see what we can do about it.

A．otherwise

B．therefore

C．anyway

D．besides

下列有关细胞色素的叙述哪项正确（）

A.全部存在于线粒体

B.都是递电子体

C.都与CO、CN一结合后丧失活性

D.都是递氢体

E.全部含有血红素辅基