We cannot figure out _______ quite a number of insects, birds, and animals are dying out.
| A．that | B．as | C．why | D．when |
We were stuck on the way to the scenic spot, otherwise we ________ lots of fun there.
| A．had had | B．have had |
| C．could have had | D．could have |
________ it rain tomorrow, we should have to put off the visit to the Yangpu Bridge.
| A．Were | B．Should |
| C．Would | D．Will |
If we had taken such effective measures much earlier, the river ________ so seriously now.
| A．is not polluted |
| B．would not be polluted |
| C．had not been polluted |
| D．would not have been polluted |
George is going to talk about the geography of his country, but I'd rather he ________ more on its culture.
| A．focus | B．focused |
| C．would focus | D．had focused |
Don't handle the vase as if it ________ made of steel.
| A．is | B．were |
| C．has been | D．had been |