Choose the letter of the implied main idea of the passage below. Dolphins use a process called sonar to find their way and to find food. They emit sound waves that bounce off
objects and return, giving the dolphin information about size, distance and density. Some scientists think the
dolphins can even "turn up" these sound waves and stun their prey. They know for sure that certain levels of
sound waves could easily kill a large squid in a matter of minutes. If these scientists are correct, dolphins
could easily kill each other—yet they don't.
Sonar can kill.
Dolphins do not kill each other.
Dolphin sonar is a powerful tool that is used with skill and care.
Sonar enables dolphins to find their way around.