I will buy you a new bike if you learn how to swim this summer. —Is that a ________? I’m sure I’ll get the bike.

This is 3-D printer. And this is an artificial (人工的) ear. Can you believe that scientists printed this artificial ear by this 3-D printer?

The city has changed little in the lastyears.

Uncle Li is hardly ever tired. He’s really .

_____frightened us ____the electricity was suddenly cut off, which threw all of us into the dark.