To use a foreign language effectively, you need to understand the culture________ it is spoken.
| A．what | B．where | C．why | D．which |
.
A proper approach to ________ your learning efficiency is of great significance to every student.
| A．improving | B．improve | C．be improving | D．having improved |
.
—Why are you looking so worried?
—I sent an email to my son in America last week, but no reply ________.
| A．was received | B．had received | C．has received | D．has been received |
.
When the environmentally friendly cars came onto the market, many people were eager to buy them ________ the price.
| A．wherever | B．however | C．whichever | D．whatever |
.
—I believe Tom to be a great businessman like Bill Gates in the future.
—Why do you think so?
—Because he is ________ in business.
| A．as hungry as a lion | B．as sharp as a spear |
| C．as busy as a bee | D．as sly as a fox |
.
Men will ________ all the natural resources if they continue consuming them like that.
| A．run out | B．wipe out | C．drop out | D．hold out |