Answer:

Explanation:
As we know that the orbital speed of the satellite is given as

also we know that
time period of the revolution is given as

now from above equation we know that


so we will have

now plug in all data in this equation


The correct answer is - a. was a sign of danger.
Once the people saw that the ocean waters are receding and were living vast space without water behind them, they knew that something big and very dangerous will happen. And in fact it did. The water that was sucked in in the place were there was a crack on the ocean floor, got shot back under big pressure and it had very big speed, as well as having waves that were destroying anything on their way.