—Have they found the lost flight MH370?

—Not yet. I’m really ______ the people on the plane.

A．worried about

B．angry with

C．careful of

D．afraid of

下述哪些属于兴奋性中枢神经递质（）

A.去甲肾上腺素

B.乙酰胆碱

C.5-羟色胺

D.门冬氨酸

E.甘氨酸