This summer vocation I am going to do a lot of _________ to prepare for the senior high school.

A．job

B．work

C．invention

D．service

铈量法选用指示剂（）

A.结晶紫

B.二甲酚橙

C.淀粉溶液

D.甲基红

E.邻二氮菲亚铁