TASK DEFINITION: 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.
PROBLEM: Question: What are drilled to monitor groundwater pollution? Answer: test wells

SOLUTION: Test wells are drilled to monitor groundwater pollution.

PROBLEM: Question: When zinc metal is mixed with sulfur and heated, what is produced? Answer: zinc sulfide

SOLUTION: Zinc sulfide zinc metal is mixed with sulfur and heated, what is produced.

PROBLEM: Question: What is a winding ridge of sand deposited by a stream of meltwater called? Answer: esker

SOLUTION:
A(n) esker is a winding ridge of sand deposited by a stream of meltwater called.