— What do you think of the film Inception (盗梦空间) ? 

— Just so-so. I don't think it worth ______ a second time.

                                                                                                                                    [ ]

A. watching

B. watched

C. to watch

D. being watched

下列常见物质中，属于纯净物的是（　　）

A．石灰水

B．蒸馏水

C．加碘食盐

D．石油