Teacher:Given a scientific passage and an answer, generate a question for the given answer.
Teacher: Now, understand the problem? Solve this instance: Passage: Left: Indrik myneur; Right: Courtesy of UNEP/GRID. Craters and rifts become lakes when they fill with water . Left: CC BY 2.0; Right: Non-copyrighted and available for free use. Answer: lakes
Student:
What do craters and rifts become when they fill with water?