Trees ____ fight air pollution．They are natural air conditioners．
A．should B．must C．need D．can
____ it snowed heavily yesterday, nobody in our class missed the lesson．
A．Though B．Because C．Unless D．Since
Tomorrow there's a programmed about our school on TV，then it ____ by millions of people．
A．will see B．saw C．will be seen D．was seen
My brother is two meters in height．It's very difficult to find clothes big enough ____ him．
A．about B．at C．with D．for
—Have you ____ joined in a dragon boat race?
—Yes，I have．
A．never B．still C．seldom D．ever
I forget to bring a pen．Would you lend me ____?
A．one B．that C．it D．this
