The energy stored in coal ______.

A.A.Plants

B.B.water

C.C.rock

D.D.creatures

A.电容两端的电压 the voltage on the capacito

B.电容的电流 the current across the capacito

C.储存的电荷 the stored charge

D.电容值 the capacitance value

A.A.are a source of stored genetic information

B.B.are the main structure of the plasma membrane

C.C.serve as source of energy

D.D.aid in the folding of proteins

A.电容两端的电压 the voltage on the capacitor

B.电容的电流 the current across the capacitor

C.储存的电荷 the stored charge

D.电容值 the capacitance value

A.电容两端的电压 the voltage on the capacitor

B.电容的电流 the current across the capacitor

C.储存的电荷 the stored charge

D.电容值 the capacitance value

Before doing any work on a hydraulic system equipped with accumulators, you should

A.drain the accumulators and purge with oxygen

B.bleed off all stored energy from the accumulators completely

C.charge the accumulators to prevent system energy loss

D.pump the hydraulic fluid into the accumulators to prevent fluid loss

Coal, oil, natural gas, and all other fuels are stored-up energy from the sun. Some was collect ed by this season's plants as carbon compounds. Some was stored by plants and trees ages ago.

Even waterpower derives from the sun. Water turned into vapor by the sun falls as rain. It courses down the mountains and is converted to electric power.

Light transmits only the energy that comes from the sun' s outer layers, and much of this energy that is directed toward the earth never arrives. About nine-tenths of it is absorbed by the atmosphere of the earth. In fact; the earth itself gets only one half-billionth of the sun' s entire output of radiant energy.

All the useful energy at the surface of the earth comes ______.

A．directly from the sun

B．from the sun' s activity

C．from energy stored by the sun

D．from radiation of the sun

A.电感两端的电压 the voltage on the inductor

B.流过电感的电流the current across the inductor

C.电感值 the inductance

D.电感体积 inductor's physical size