________ some students are not aware of is ________ difficult life can be if they are not devoted to study.
| A．That; how | B．Which; what |
| C．What; what | D．What; how |
---What do you think made the woman so upset？
--- _____ weight.
| A．As she put on | B．Put on |
| C．Putting on | D．Because of putting on |
The research is so designed that once ____ nothing can be done to change it.
| A．begins | B．having begun | C．beginning | D．begun |
______ in thought, he almost ran into the car in front of him.
| A．Losing | B．Having lost | C．Lost | D．To lose |
Not only ____ the jewelry she ____ been sold for her son's gambling debts but also her house．
| A．is；has | B．has；had | C．has；has | D．／；has |
The man whose songs we are fond of ____ in our city next week．
| A．singing | B．to sing | C．will sing | D．sang |