---What did our teacher do?

---He raised his arm as a(n)        for us to stop.

A．signal

B．advice

C．evidence

D．design

测定肾小球滤过率的理想试剂是（）

A.菊粉

B.肌酐

C.葡萄糖

D.尿素氮

E.对氨马尿酸