Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
--------
Question: Simple kind of diffusion do small hydrophobic molecules squeeze through lipid molecules.

Answer: What kind of diffusion do small hydrophobic molecules squeeze through lipid molecules?


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: Genes are composed of dna.

Answer:
What are genes composed of?