In the global economy, a new drug for cancer, _________ it is discovered, will create many economic possibilities around the world.
| A．whatever | B．whoever | C．wherever | D．whichever |
__________ out of work for a few months, mother took up the job of waiting on patients in the hospital.
| A．To be | B．Being | C．Having been | D．Having |
__________ in the restaurant for half an hour, I suddenly realized I had left my wallet at home.
| A．To wait | B．Having waited | C．Having been waited | D．To have waited |
The young man, __________ abroad for two years, decided to go back to his motherland.
| A．to work | B．working | C．having worked | D．to have worked |
Tom returned from the manager's office, __________ me that the boss wanted to fire me.
| A．having told | B．tells | C．to tell | D．telling |
__________ the task, they had to stay in the lab for another two hours.
| A．Not completing | B．Not completed |
| C．Not having completed | D．Having not completed |