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

[EX Q]: Passage: The embryo develops from a fertilized egg. While still inside the seed, the embryo forms its first leaf (cotyledon) and starts to develop a stem (hypocotyl) and root (radicle). Answer: cotyledon
[EX A]: What is the name of the first leaf developed inside an embryo?

[EX Q]: Passage: Photography by Kat. Ferns are common in the understory of the tropical rainforest . CC BY 2.0. Answer: understory
[EX A]: In a tropical rainforest, where are ferns common?

[EX Q]: Passage: An unconformity is a gap in rock layers. They occur where older rock layers eroded away completely before new rock layers were deposited. Answer: an unconformity
[EX A]:
What is a gap in rock layers called?