Radium salts，which have been found to ______ in bones，give rise to bone cancer.
| A．pile up | B．build up | C．keep up | D．pull up |
--Could you do me a favor?
--It depends on _____it is.
| A．which | B．whichever | C．what | D．whatever |
_____at what he said,she asked him why he said so to her.
| A．Amazing | B．Amazed | C．Having amazed | D．Surprised |
Soon , Mary _____ the shock and became calm again.
| A．recovered | B．recovered from | C．affected | D．covered from |
The children were surprised by the sudden _____ of their teacher.
| A．enter | B．entrance | C．entry | D．come |
—Do you think we can get there on time?
—Yes,_________ the bus does not break down.
| A．even if | B．unless |
| C．until | D．so long as |