instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Seismologists originally measured the intensity of an earthquake with the mercalli scale.
answer:
How did seismologists originally measure the intensity of an earthquake?


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


question:
Trees send out rootlike extensions that produce new stems is an example of asexual reproduction.
answer:
Which of the following is an example of asexual reproduction?