10. Some species of dolphins find their prey by echo-
location; they emit clicking sounds and listen for
echoes returning from distant objects in the water.
Marine biologists have speculated that those same
clicking sounds might have a second function:
particularly loud clicks might be used by the
dolphins to stun their prey at close range through
Which of the following, if discovered to be true,
would cast the most serious doubt on the correctness
of the speculation described above?
(A) Dolphins that use echolocation to locate distant
prey also emit frequent clicks at intermediate
distances as they close in on their prey.
(B) The usefulness of echolocation as a means of
locating prey depends on the clicking sounds
being of a type that the prey is incapable of
perceiving, regardless of volume.
(C) If dolphins stun their prey, the effect is bound
to be so temporary that stunning from far
away, even if possible, would be ineffective.
(D) Echolocation appears to give dolphins that use
it information about the richness of a source
of food as well as about its direction.
(E) The more distant a dolphinâ€™s prey, the louder
the echolocation clicks must be if they are to
reveal the preyâ€™s presence to the hunting