单选题
The idea of a fish being able to generate
electricity strong enough to light lamp bulbs—or even to run a small electric
motor—is almost unbelievable, but several kinds of fish are able to do this.
Even more strangely, this curious power has been acquired in different ways by
fish belonging to very different families. Perhaps the best
known are the electric rays, or torpedoes (电鱼), of which several kinds live in
warm seas. They posses on each side of the head, behind the eyes, a large organ
consisting of a number of hexagonal shaped cells rather like a honeycomb. The
cells are filled with a jelly-like substance, and contain a series of fiat
electric plates. One side, the negative side, of each plate, is supplied with
very fine nerves, connected with a main nerve coming from a special part of the
brain. Current passes from the upper, positive side of the organ downwards to
the negative, lower side. Generally it is necessary to touch the fish in two
places, completing the circuit, in order to receive a shock.
The strength of this shock depends on the size of the fish, but newly born ones
only about 5 centimeters across can be made to light the bulb of a pocket
flashlight for a few moments, while a fully grown torpedo gives a shock capable
of knocking a man down, and, if suitable wires are connected, will operate a
small electric motor for several minutes. Another famous
example is the electric eel. This fish gives an even more powerful shock. The
system is different from that of the torpedo in that the electric plates run
longitudinally (纵 向) and are supplied with nerves from the spinal (脊骨) cord.
Consequently, the current passes along the fish from head to tail. The electric
or gans of these fish are really altered muscles and like all muscles are apt
(likely)to tire, so they are not able to produce electricity for very
long. The power of producing electricity may serve these fish
both for defence and attack.
单选题
It can be seen from the passage that ______.
A. the torpedo's electric cells have a shape with six sides
B. some fish can produce enough electricity to drive a number of electric
motors
C. the current travels in an upward direction from the positive side to
negative side in torpedo's electric cells
D. the capacity to generate electricity is the distinctive characteristic of
the fish
【正确答案】
A
【答案解析】[解析] 参考文章第二段“...rather like a honeycomb”，“外形像蜂窝”可知电池是六边形的。
单选题
Usually you will not get a shock by touching the electric ray in one
place only because ______.
A. a torpedo's electric cells contain more than one electric plates
B. to complete the circuit, you have to touch the fish in two places
C. the current in one place is not strong enough to give a shock
D. the fish's electric cells are filled with jelly-like substance
【正确答案】
B
【答案解析】[解析] 参考文章第二段最后一句。
单选题
The main idea of the third paragraph is that ______.
A. the mass of the fish decides the intensity of electric power it
generates
B. the strength of shock given by a young electric ray can only light the
bulb of a pocket flashlight
C. to make full use of the energy produced by electric fish, suitable wires
should be available
D. a mature torpedo is capable of producing enough electricity to knock down
a man
【正确答案】
A
【答案解析】[解析] 本段第一句说明的主旨，即电击的强度取决于鱼的尺寸。可知A项最合适。
单选题
The reason why the electric eel is able to give more powerful shock is
that ______.
A. compared with those in the torpedo, the working system of electric plates
in the eel is more direct and efficient
B. compared with other electric fish, the eel possesses much more electric
plates
C. the working system of the electric plates in the eel is far inferior to
those in the torpedo
D. the working system of the electric plates in the eel is the most
effective