___ waiting for the bus.
| A．They both are | B．They are both | C．They both will be | D．Both they are |
My sister，an inexperienced rider，was found sitting on the bicycle _________ to balance it．
| A．having tried | B．trying |
| C．to try | D．tried |
_________ in the fields on a March afternoon，he could feel the warmth of spring．
| A．To walk | B．Walking |
| C．Walked | D．Having walked |
_________ to reach them on the phone，we sent an email instead．
| A．Fail | B．Failed |
| C．To fail | D．Having failed |
We went right round to the west coast by __________ sea instead of driving across _________ continent. 
| A．the … the | B．/ … the | C．the … / | D．/ … / |
In____review of 44 studies, American researchers found that men and women____who ate six key foods daily cut the risk of ______ heart disease by 76%. 
| A．a; the | B．the; a | C．a; 不填 | D．不填； a |