---May I use your computer, Alex?
---Sorry. Mine _____.
| A．has repaired | B．is being repaired | C．has been repaired | D．is repairing |
_________ around the Water Cube，we were then taken to see the Bird’s Nest for the 2008 Olympic Games．
| A．Having shown |
| B．To be shown |
| C．Having been shown |
| D．To show |
He was busy writing a story，only _________ once in a while to smoke a cigarette．
| A．to stop | B．stopping |
| C．to have stopped | D．having stopped |
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 |