Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Problem:Passage: To grow and develop, you must form new cells. Imagine how often your cells must divide during a growth spurt. Growing just an inch requires countless cell divisions. Your body must produce new bone cells, new skin cells, new cells in your blood vessels and so on. Answer: cells
Solution:
A growth spurt requires constant divisions of what?