English is difficult __________ well in a short time.
| A．to learn | B．learning |
| C．to be learned | D．learn |
is even more important is the earth cooled down, water began to appear on its surface.
| A．When; that; when | B．What; whether; as | C．What; that; as | D．lt; whether;  as |
Going on a trip into space must be quite exciting experience.
| A．/;the | B．the; the | C．the; an | D．/; an |
Though having lived abroad for years, many Chinese stillthe traditional customs.
| A．perform | B．pssess | C．observe | D．support |
He is still his story that his car was stolen and later returned, but the police don’t believe him at all.
| A．agreeing on | B．dealing with | C．thinking about | D．sticking to |
—Mum, I will leave for tha party.
—Remember your .thank your friend when you leave the party.
| A．action | B．polite | C．manner | D．manners |