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

[Q]: Passage: You consist of a great many cells, but like all other organisms, you started life as a single cell. How did you develop from a single cell into an organism with trillions of cells? The answer is cell division. After cells grow to their maximum size, they divide into two new cells. These new cells are small at first, but they grow quickly and eventually divide and produce more new cells. This process keeps repeating in a continuous cycle. Answer: cell division
[A]: What process allows an individual to develop from a single cell into an organism with trillions of cells?

[Q]: Passage: Climate is the most important factor in determining the type of soil that forms in a particular area. Answer: climate
[A]: What is the most important factor in determining the type of soil that forms in a particular area?

[Q]: Passage: Cardiac muscle undergoes aerobic respiration patterns, primarily metabolizing lipids and carbohydrates. Myoglobin, lipids, and glycogen are all stored within the cytoplasm. Cardiac muscle cells undergo twitch-type contractions with long refractory periods followed by brief relaxation periods. The relaxation is essential so the heart can fill with blood for the next cycle. The refractory period is very long to prevent the possibility of tetany, a condition in which muscle remains involuntarily contracted. In the heart, tetany is not compatible with life, since it would prevent the heart from pumping blood. Answer: cardiac muscle
[A]:
What kind of muscle cells undergo twitch-type contractions with long refractory periods followed by brief relaxation periods, allowing the heart to fill with blood for the next cycle?