Given a scientific passage and an answer, generate a question for the given answer.

Ex Input:
Passage: The problem doesn't stop with plowing. Crops are usually planted in rows, with bare soil in between the rows. In places where crops grow only during part of the year, the land may be bare for a few months. Answer: months

Ex Output:
In places where crops grow only during part of the year, the land may be bare for a few?

Ex Input:
Passage: Adolescents may have mood swings because of surging hormones. Answer: surging hormones

Ex Output:
Many adolescents experience frequent mood swings. name one of the causes for this.

Ex Input:
Passage: Water is the most common substance on Earth, and most of it exists in the liquid state. A liquid is one of four well-known states of matter, along with solid, gas, and plasma states. The particles of liquids are in close contact with each other but not as tightly packed as the particles in solids. The particles can slip past one another and take the shape of their container. However, they cannot pull apart and spread out to take the volume of their container, as particles of a gas can. If the volume of a liquid is less than the volume of its container, the top surface of the liquid will be exposed to the air, like the vinegar in the bottle pictured in the Figure below . Answer: liquid

Ex Output:
The most common substance on earth, water, is primarily present in what state?