Passage 3

　　Hamletfish are cautious lovers. Each evening at twilight, many times an evening in fact, a pair of them will leave the safety of their Caribbean reef and rush a few yards off the seafloor. Positioning themselves side-to-side, head-to-tail they hurriedly release their eggs and sperm. Then they turn sharply for home, leaves their gametes to mix in silence.

　　Ichthyologist Phillip Lobel of the Woods Hole Oceanographic Institution has found that hamlet fish and many other fish emit“cries of ecstasy" at the appropriate moment.

　　Biologists have long known that a few fish make sounds. The toadfish, for example, is named for its low call, which can be heard even above water. Underwater, however, human ears don't work well. As a result researchers didn't notice how common fish calls were until Lobel started diving with a video camera and an underwater microphone like the kind the Navy uses to listen for submarines.

　　Lobel has learned that the fish playing the role of the male-hamletifish switches roles from one tryst to the next-emits a series of short, low sounds. The female responds with a downward, sweeping sound like a slide whistle. The purpose to these calls, says Lobel, is probably to synchronize spawning, so that sperm and egg have a fighting chance of actually meeting in the water.

　　Then, at the moment of spawning, the female flutters her pectoral fins, contracts her abdominal muscles to squeeze out the eggs, and lets out a soft cry, which in part may simply be the sound of her swim bladder vibrating from all that muscle contraction.“The sound is not a scream, it's only as loud as conversation," says Lobel.

　　Lobel has since recorded sounds from about two dozen other fish species. He thinks fish calls, like some birdcalls, may be a means by which fish recognize suitable mates, and that fish of the same species may even communicate in regional dialects.“Lots of people sit and watch their little fish in their aquarium," Lobel says,“Well, it's like looking at a birdcage behind sound-proof glass. These things are all making sounds."

　　11. The primary purpose of this passage is to .A.refute a misconception that fish don't make soundsB.prove a new discoveryC.explain the time when hamletfish make soundsD.demonstrate the fact that fish are romantic as human beings

　　12. Which of the following is NOT true about fish calls according to this passage?A.Fish calls are commonly regarded as rare.B.Some of sounds produced by fish are not uttered from their mouths.C.Fish calls may be a means by which fish found their mates.D.No sounds can be heard from fish if a person stands on the ground.