The air in Rizhao is getting much _____ now than a few years ago .

“What will you do during the summer holiday”— “I don’t know, but it’s high time _____something.”

下列各句中，没有语病的一句是

I shall never forget the day ________ Shen Zhou V was launched, ________ has a great effect on my life.

________ excited Geoff Marcy most was whether there were planets in other solar system where life might exist