Everyone should play a part_____the earth.
A．to save B．saved
C．for saving D．in saving
Please check your paper to ________ there are no mistakes.
A．think of B．try out C．find out D．make sure
Liu Xi's father kept on____although he was tired.
A．to sleep B．sleeping C．to work D．working
World Cup host Brazil would like to help China________China's soccer.
A．improve B．send C．question D．discuss
Mrs. Green promised____all she can to help us.
A．knowing B．to know C．doing D．to do
Dale is studying in________university and he wants to be________engineer.
A．a，a B．a，an C．an，a D．an，an
