As a science lover, I hope I can invent a bike ________ can fly in the sky.
where
when
which
who
The underlined part in the word “houses” is pronounced as .
—Do you know when World Non-smoking Day is?—_____________.
如果你想知道对方姓什么时,你应该问_____________________________
---Wow! These inventions are amazing.—They were all invented _______years ago.
---Mary is a careful girl.---Yes. She always goes over her exercises to there are no mistakes.