Answer:
C. Seriously
Explanation:
If you replace "gravely" with each of the answers, seriously makes more sense :)
If we are going to unscramble the given set of letters above, the word that would be formed is "BATHYMETER". So a bathymeter is a device <span>used to measure the depth of water in oceans, seas, or lakes. Hope this answers your question. Have a great day!</span>