In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

Question: What do ecosystems absorb on the earth? Answer: energy
Energy do ecosystems absorb on the earth.

Question: Which are the closest living relations to land plants? Answer: charophytes
Charophytes are the closest living relations to land plants.

Question: What is heard when sound waves bounce back from a surface that they can't pass through? Answer: echo

A(n) echo is heard when sound waves bounce back from a surface that they can't pass through.