In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

Question: Why do birds need a light-weight body? Answer: to stay aloft
Birds need a light-weight body for to stay aloft.

Question: What is the name for a series of changes in the reproductive system of mature females that repeats every month on average? Answer: menstrual cycle
Menstrual cycle is the name for a series of changes in the reproductive system of mature females that repeats every month on average.

Question: Insulin is made up of how many polypeptide chains? Answer: two

Insulin is made up of two polypeptide chains.