instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
The long, threadlike extensions of the nerve cell help transmit nerve impulses.
answer:
Which part of the nerve cell helps transmit nerve impulses?


question:
Energy do ecosystems absorb on the earth.
answer:
What do ecosystems absorb on the earth?


question:
All mammals have four limbs.
answer:

How many limbs do all mammals have?