instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Three many families are known quarks divided into.
answer:
How many families are known quarks divided into?


question:
Together, the muscular and skeletal organs are known as the musculoskeletal system.
answer:
Together, the muscular and skeletal organs are known as what?


question:
Birds need a light-weight body for to stay aloft.
answer:

Why do birds need a light-weight body?