单选题 Directions : Read the
following text. Choose the best word or phrase for each numbered blank and mark
A, B, C or D on ANSWER SHEET 1.
In addition to the established energy
sources such as gas, coal, oil and nuclear, there are a number of other sources
that we ought to consider. Two of these are hydroelectric and tidal
power. These two sources are {{U}}(21) {{/U}} in that
they are both renewable. {{U}}(22) {{/U}}, hydropower is more widely
used than tidal. In {{U}}(23) {{/U}}, a substantial amount of
electricity is already produced in HEP (hydroelectric power)stations worldwide,
{{U}}(24) {{/U}} tidal stations are still in the very early
{{U}}(25) {{/U}} of development. As far as geographical
{{U}}(26) {{/U}} is concerned, HEP projects are to be found on lakes and
rivers, while tidal {{U}}(27) {{/U}} are constructed only at river
mouths where tidal {{U}}(28) {{/U}} is great. Unfortunately these are
{{U}}(29) {{/U}} in number. At present HEP stations are found mainly in
Norway, Canada, Sweden and Brazil, whereas tidal plants are in {{U}}(30)
{{/U}} in France, Russia and China. As regards capital
{{U}}(31) {{/U}}, both require very high investment. On the other hand,
generating {{U}}(32) {{/U}} are quite low in both cases. In fact, a
large scale HEP plant is capable of producing power more {{U}}(33)
{{/U}} than conventional sources, such as coal, oil and nuclear plants.
Tidal power also compares {{U}}(34) {{/U}} with nuclear and oil
generated electricity, {{U}}(35) {{/U}} the amount of money on
production. {{U}}(36) {{/U}} HEP stations, tidal constructions have a
long life {{U}}(37) {{/U}}. It is estimated that they can operate for
over 100 years. With respect to {{U}}(38) {{/U}} of supply, tidal
stations {{U}}(39) {{/U}} from HEP ones in that they often can only
supply power {{U}}(40) {{/U}}. HEP stations, however, provide a constant
supply of electricity.