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

[EX Q]: Passage: Waves are characterized by their ability to constructively and destructively interfere . Light waves which interfere with themselves after interaction with a small aperture or target are said to diffract . Answer: diffract
[EX A]: Light waves which interfere with themselves after interaction with a small aperture or target are said to what?

[EX Q]: 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 A]: In places where crops grow only during part of the year, the land may be bare for a few?

[EX Q]: Passage: All compounds form when atoms of different elements share or transfer electrons. In water, the atoms share electrons. In some other compounds, called ionic compounds , atoms transfer electrons. The electrons actually move from one atom to another. When atoms transfer electrons in this way, they become charged particles called ions. The ions are held together by ionic bonds. Answer: ions
[EX A]:
When electrons move from one atom to another, they become what?