单选题 Although vocal cords are lacking in cetaceans,
phonation is undoubtedly centered in the larynx.
The toothed whales or odontocetes (sperm whale
Line and porpoises) are much more vociferous than the
(5) whalebone whales, or mysticetes. In this country
observers have recorded only occasional sounds
from two species of mystieetes (the humpback and
right whale). A Russian cetologist reports hearing
sounds from at least five species of whalebone
(10) whales but gives no details of the circumstances or
descriptions of the sounds themselves. Although
comparison of the sound-producing apparatus in
the two whale groups cannot yet be made, it is
interesting to note that the auditory centers of the
(15) brain are much more highly developed in the odon-
tocetes than in the mysticetes, in fact, to a degree
unsurpassed by any other mammalian group.

单选题 The passage contains information that would answer which of the following questions?
Ⅰ. What are odontocetes and mysticetes?
Ⅱ. In which part of the body do whales produce sounds?
Ⅲ. In which animals is the auditory center of the brain most developed?

单选题 The author's attitude toward the observations reported by the Russian cetologist mentioned in lines 8-11 is best described as one of

单选题 It can be inferred from the passage that