Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Ex Input:
Oxygen gas is given off by plants.

Ex Output:
Which gas is given off by plants?


Ex Input:
Gastric emptying is regulated by both the stomach and the duodenum.

Ex Output:
Gastric emptying is regulated by both the stomach and what other digestive structure?


Ex Input:
A grain of pollen can be described as a tiny male gametophyte enclosed in a tough capsule.

Ex Output:

What can be described as a tiny male gametophyte enclosed in a tough capsule?