instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Some viruses carry a few viral enzyme molecules within their capsids.
answer:
Some viruses carry a few viral enzyme molecules within their what?


question:
The main advantage of urea is its very low toxicity.
answer:
The main advantage of urea is its very low what?


question:
Medulla is the spinal trigeminal nucleus located.
answer:

Where is the spinal trigeminal nucleus located?