根据下列文章,请回答 31～35 题。
Regeneration of Limbs
Most people would agree that it would bewonderful if humans could regenerate limbs．Those who have lost their arms orlegs would be complete again．The day is still far off when this might happen．Butin the last l o years，doctors have reported regeneration in smaller parts of the body,most often fingers．
Regeneration is not a newly-discoveredprocess．For centuries，scientists have seen it work in some kinds of animals．Breakoff a lizard's(蜥蜴的)tail，for example，and it will grow a new tail．Scientists noware looking for a way to turn on this exciting ability in more highly-developedanimals，including humans．Their experiments show that nerves，cell chemistry andthe natural electric currents in the body all seem to have a part in this process．
The body of every animal contains generalpurpose cells that change into whatever kind of cells the body needs．Animalssuch as the lizard or salamander(蝾螈)use these cells to regenerate a new tail．orleg when the old one is broken off．These cells collect around the wound．Theyform. a mass called a blastema(胚基)．The cells of the blastema begin to change．Somebecome bone cells，some muscle cells，some skin cells．Slowly，a new part regrowsfrom the body outward．When completed．the new part is just like the old one．
More than 2oo years a9o。Italian scientistLuigi Spallanzani showed that younger animals have a greater ability toregenerate lost parts than older animals。So do animals lower on the ladder ofevolutionary development．The major difference seems to be that less-developedanimals have more nerves in their tails and legs than humans do in their armsand legs．
Another helpful piece of information wasdiscovered in the late l 8oos．Scientists found that when a creature is injured．anelectrical current flows around the wound．The strength of the current dependson how severe the wound is and on how much nerve tissue is present．
In l 945，American scientist Meryl Rosetested another idea about regeneration．He thought a new limb might grow onlyfrom an open wound．Doctor Rose cut off the front legs of some frogs，below theknee．He kept the wounds wet with a strong salty liquid．This prevented skin fromgrowing over the wounds．The results were surprising．Frogs do not regenerate newlegs naturally．But these frogs began to grow new limbs．About half of eachcut—off leg grew back again．New bones and muscles developed．
This research has led doctors to new waysof treating cut-off fingers．Doctors have observed，for example，that manychildren and some adults will regrow the top of a finger if the wound is leftopen．
第 31 题 The passage indicates that

A. humans can never regenerate limbs．
B. humans might be able to regenerate limbsin the future．
C. human limbs may be regenerated on someanimals first．
D. regeneration of human limbs will SOON become a reality．