The problem of underground water is more serious because（ ）

[A] the underground water trickles away all the year round

[B] the underground water is hidden deep beneath the Earth

[C] the change of it must be controlled by the NASA's satellites

[D] the dramatic change of it might affect the gravitational field

[单选题]In a complete oil/water separator, more oil will separate out onto the underside of these plates and travel outwards until it is free to rise into the oil collecting space Whats the meaning of "it" in the sentence above?（）A . a separatorB . oilC .

[单选题]（） water is more expensive than fresh water It has high specific heat and low viscosity.A . DistilledB . DistillingC . BoilingD . Boiled

[问答题]The doctor told me to have more water.

[问答题]The doctor told me to have more water.

[问答题]The doctor told me to have more water.

[问答题]Air pollution is more serious than water pollution.

[问答题]Air pollution is more serious than water pollution.

[问答题]The undersea world is very beautiful.Now more and more people want to divei

[名词解释] 地道 underground path

[主观题]Underground－economy 地下经济