Is air the lightest thing in the world?– Not . Scientists from Zhejiang University have just developed the world’s lightest material.

Bob swims ________ than I, but he doesn’t swim_________ my brother.

Can you help me with the bike? — Sorry, I’m a little busy now. Read the instruction. It______, “Do it yourself”.

Go ______ the bridge. You’ll find the library on the left.[ ]

Have you ever _______ to Singapore?–No, never.