We paddled over and climbed on to the steamboat, as quiet as mice.
| A．kept | B．keeping |
| C．to keep | D．keep |
The Japanese government stubbornly claimed the ownership of DiaoYu Islands belonging to China,___greatly hurt the friendship between the two peoples
| A．that |
| B．it |
| C．this |
| D．which |
Helen was much kinder to her youngest son than to the others,___,of course,made the others envy him
| A．who |
| B．that |
| C．what |
| D．which |
At the beginning of the twentieth century,___the population all over the world?
| A．what was |
| B．what were |
| C．how many are |
| D．how much is |
Most environmental problem exist because___measures for preventing them were not taken in the past
| A．adequate |
| B．enough |
| C．many |
| D．much |
He talked happily about the men and the books___interested him greatly in the school
| A．which |
| B．that |
| C．who |
| D．when |