China is one of the countries ________ the Mekong River flows.
| A．in which | B．by which |
| C．across which | D．through which |
______ you’re tried it, you can’t imagine how pleasant it is.
| A．When | B．Although | C．Because | D．Unless |
For miles around me there was nothing but a desert, without a single plant or tree ______.
| A．on earth | B．in sight | C．at a distance | D．in place |
More and more people choose to shop in a supermarket as it offers a great ____ of goods.
| A．expression | B．mixture | C．variety | D．combination |
So difficult ______ it to live in an English-speaking country that I determined to learn English.
| A．did I feel | B．I have felt | C．have I felt | D．I did feel |
For a moment nothing happened. Then ______all shouting together.
| A．voices had came | B．did voices come | C．came voices | D．voices would come |