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:
Digestion begins in the gastrovascular cavity.
answer:
Where does digestion begin?

question:
Viruses biological agents that infect living hosts contain dna, yet lack the other parts shared by all cells, including a plasma membrane, cytoplasm, and ribosomes.
answer:
What biological agents that infect living hosts contain dna, yet lack the other parts shared by all cells, including a plasma membrane, cytoplasm, and ribosomes?