下列做法中用到物质氧化性的是[ ]

A．明矾净化水

B．纯碱除去油污

C．臭氧消毒餐具

D．食醋清洗水垢

The firing of a red star signal may mean（）.

A.This is the best place to land

B.You are seen - assistance will be given as soon as possible

C.Tail block is made fast

D.Slack away