instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Gastro-esophageal sphincter sphincter is located at the stomach end of the esophagus and opens to allow the bolus to enter the stomach.
answer:
Which sphincter is located at the stomach end of the esophagus and opens to allow the bolus to enter the stomach?

question:
The two parameters used to measure changes in ecosystems are resistance and resilience.
answer:
The two parameters used to measure changes in ecosystems are resistance and what related factor?

question:
Recrystallization is a process that can remove what, contaminants result when compounds are synthesized.
answer:
Recrystallization is a process that can remove what, which result when compounds are synthesized?