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

Input: Consider Input: Passage: Heat waves have increased in frequency and duration in recent years. The summer 2011 North American heat wave brought record temperatures across the Midwestern and Eastern United States. Many states and localities broke records for temperature and for the most days above 100 o F. Answer: cell membrane

Output: What are all cells surrounded by?

Input: Consider Input: Passage: When electrons are removed from an atom, that process requires energy to pull the electron away from the nucleus. Addition of an electron releases energy from the process. Answer: energy

Output: What is required when electrons are removed from an atom, and released from the process when an electron is added?

Input: Consider Input: Passage: Like all chordates, vertebrates are animals with four defining traits, at least during the embryonic stage. The four traits are:. Answer: embryonic
Output: Like all chordates, vertebrates are animals with four defining traits, at least during which stage?