Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: The sum of the masses of the atoms in the formula is referred to as molecular mass.

Answer: The sum of the masses of the atoms in the formula is referred to as what?


Question: If an air mass forms over an ocean it is called a maritime air mass.

Answer: If an air mass forms over an ocean it is called what type of air mass?


Question: Vaccine is a preventative measure that is often delivered by injection into the arm.

Answer:
What preventative measure is often delivered by injection into the arm?