题目内容：

Besides providing a perfect environment for sea plants and animals to live in, seawater has other values, one of which is that it constantly moves, and its movements produce energy.

The most obvious movements are the waves and the tides. Winds cause the waves, and the gravitational pull of the moon and the sun causes the tides. In places like the Bay of Fundy in Canada, the difference between the high and low tide level can be as much as 40 feet.

France and Britain are now trying to use energy in the tides to produce electricity. Waves can produce electricity and some experiments are taking place to learn more about this. One of the most encouraging areas of research uses the difference between the temperature of seawater at the surface and deep down to produce electricity. 

1.Waves and tides are caused by ________ .

A．the same forces

B．different forces

C．their own movements

D．plants and animals

2.It can be inferred from the passage that __________ .

A．waves as well as the energy in the tide can produce electricity

B．the highest tide is 40 feet higher than the lowest one at the sea

C．many countries in the world have made the most of energy produced by seawater

D．it is being tried in some developed countries to use energy in the tides to produce electricity

3. The best title for the passage is ______.

A．Tides and Waves

B．How to Produce Electricity

C．Seawater

D．Another Cheap Energy