下列各项不可以表达盈亏平衡点的是（)。 a．产量 b．质量 c．产品售价 d．单位可变成本

One reason for water shortage is that ______.

A．people in Europe don't turn off their taps

B．people drill too many wells and pollute them

C．the population has been continuously rising

D．there is not much underground water

A．the small amount of fresh water is constantly being replaced by rainfall

B．some of the water has been polluted

C．our need for fresh water is increasing rapidly

D．huge amount of the water on earth is seawater

We may face a severe worldwide water shortage in the future because ______.

A．some of it has been polluted

B．the small amount of fresh water is constantly being replaced by rainfall

C．our need for fresh water is increasing rapidly

Which of the following shows that water quality has improved？

A．Fish and birds show residues of heavy metal.

B．Toronto has grown salmon successfully in its waters.

C．Farming has prospered in the lakeside areas.

D．Lake water has been drawn for use by the population.

There has been a nation-wide shortage of building materials, ()which the trade is only just recovering.

A. for

B. on

C. at

D. from

There has been a nation-wide shortage of building materials, ()which the trade is only just recovering.

A．for

B．on

C．at

D．from

There has been a nation-wide shortage of building materials，()which the trade is only just recove- ring．

A．for

B．on

C．at

D．from

Equipment not ______ official safety standards has all been removed from the workshop.

A．conforming to

B．consistent with

C．predominant over

D．providing for

Equipment not ______ official safety standards has all been removed from the workshop.

A．conforming to

B．consistent with

C．predominant over

D．providing for

Statistics show that English has a vocabulary of about ______.

A．500,000 words

B．350,000 words

C．750,000 words

D．1,000,000 words