Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Example Input: On a global scale, plants and other photosynthetic organisms have generated all of the oxygen in the air.
Example Output: On a global scale, plants and other photosynthetic organisms have generated all of what element in the air?

Example Input: Deep currents are caused by differences in density at the top and bottom of the ocean.
Example Output: What is caused by differences in density at the top and bottom of the ocean?

Example Input: A(n) orangutan generally lives alone.
Example Output:
Which primate group generally lives alone?