Of all the methods they provided, ______ is of any help for solving the math problem.
| A．nothing | B．neither | C．none | D．no one |
. Don't bother Tom, he is with the experiment on water molecules in the lab.
| A．focused | B．fixed | C．occupied | D．concentrated |
It’s____ comfort to know that so many people are donating money and food to the people in need.
| A．/, the | B．a, the | C．a, / | D．/, a |
_________ the project in time, the workers were working at weekends.
| A．Completing | B．Having completed | C．To have completed | D．To complete |
. _________ many times, he finally understood it.
| A．Told | B．Telling | C．Having told | D．Having been told |
The chairman thought _________ necessary to invite Professor Smith to speak at the meeting.
| A．that | B．it | C．this | D．him |