You will be given a definition of a task first, then some input of the task.
In this task, you are given a sentence and a question, you would be asked to create the answer which is contained in the sentence provided.

Sentence: A tracer is the name for a substance that can be used to follow the pathway of that substance through some structure. Question: What is the name for a substance that can be used to follow the pathway of that substance through some structure?
Output:
tracer