Il. Multiple-choice cloze: Choose the best answer for each blank. (40 points； 2 points each)
Take one look at a ghost shark and you may say, "What's up with that weird-looking fish?"Over the past few decades, scic ientists learned that these cartilaginous fishes,ratfish or Chimaeras, have been around__22__ hundreds of millions of years, and that they havevenomous spines in front of their dorsal fins and 'fly" through the water by flapping their pectoralfins. They even learned that most male ghost sharks have a retractable sex organ on their foreheadsthat resembles a medieval mace.
However, __23__ remains to be learned about these strange creatures. Basic biologicalinformation, like how long they live and how ofen they reproduce, is lacking for most of the 52known species. The_24_. of this key information makes it difficult for scientists to manage andmonitor ghost shark populations, even as evidence mounts that some species may be_25_ of extinction.
【題組】21.
(A) also
(B) yet
(C) despite
(D) whereas