---Have you heard about Volunteer?
---Sure, A volunteer is someone _________ is willing to offer help without being paid..
| A．who | B．what | C．where | D．which |
Newton was playing under an apple tree ____ an apple fell onto his head.
| A．when | B．while |
| C．after | D．before |
Which of the diagrams below shows the air temperature of Beijing in a year?
______ great scientist Qian Xuesen is!
| A．How | B．How a |
| C．What | D．What a |
I don’t know when he ______. When he ______, I will let you know.
| A．will arrive, will arrive |
| B．arrives, arrives |
| C．will arrive, arrives |
| D．arrives, will arrive |
------Whose shirt is this?
------ It _______ be Li Lei’s. It is too big for him.
| A．could | B．must |
| C．can’t | D．might |