A、They were frightened and distressed. B、They swam away when the speaker was turned on. C、They swam closer to "examine" the spea

A team of scientists recently began a project to measure the effects of loud noises on sea animals. If the sounds don’t harm the animals, then the researchers can go ahead with a plan to transmit sound waves through the Pacific Ocean to take the earth’s temperature. Sound travels faster through warm water than cold water. By analyzing the speed of sound through the ocean over, the scientists will be able to determine if our planet is warming up. The experiment was nearly cancelled more than a year ago because environmental groups fear that the sound will harm the sea animals. So, scientists are conducting tests on the animals first. The researchers lowered a loud speaker that emit low frequency sound about 1,000 meters beneath the ocean. Scientists at the site transmit sound waves into the ocean. Radio transmitters attached to some of the sea animals help the researchers keep track of the animals’ movements. If the sea animals are distressed by the sounds, they would swim away from the speakers. So far, there aren’t any signs that the animals are being harmed. Researchers at the site noticed that large numbers of sea animals swim near the speaker whether it was turned on or off, but it is still too soon to know for sure, the scientists admit.
Questions 16 to 18 are based on the passage you have just heard.
16. What is the purpose of analyzing the speed of sound through the Pacific Ocean?
17. For what purpose were radio transmitters used?
18. What was the reaction of the sea animals to the sound tests’?