instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Resonance is the term for the use of two or more lewis structures to represent the covalent bonding in a molecule.
answer:
What is the term for the use of two or more lewis structures to represent the covalent bonding in a molecule?


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


question:
Tight junction is the term for a watertight seal between two adjacent animal cells.
answer:

What is the term for a watertight seal between two adjacent animal cells?