You click your fingers in a large hall and hear the echo 0.5 seconds later off the back wall. How far is the back wall? A boat send a sound to the bottom of the ocean and it takes 2 seconds to return to the boat. How deep in the ocean?

Please answer the questions above for 15 points, help desperately needed!:)

How does a circuit breaker protect a refrigerator? a. when the current is too high, a metal strip in the fuse melts and opens the circuit. b. when the resistance is too high , a re-settable which opens a circuit c. when the current is too high , a re-settable switch opens the circuit d. when the resistance is too high a metal strip in the fuse melts and opens the circuit