The discovery of how bronze is made was probably accidental, but it     

to be an important event.

A．turned over

B．turned about

C．turned out

D．turned off

金葡菌产生的酶和毒素不包括（）。

A.血浆凝固酶

B.α－溶血素

C.杀白细胞素

D.内毒素

E.肠毒素