Answer: A (Molecular Formula)
Explanation: it is necessary to know the molar mass of the compound. Chemists use an instrument called a mass spectrometer to determine the molar mass of compounds, which requires the Molecular Formula to be completed.
<span>A lime is called a lime because it's lime in colour and a lemon is called lemon because it's lemon in colour. Just to change the subject slightly why is a fly called a fly? - because it flies - so if a fly didn't have wings would it be called a walk. We could go on and on with this couldn't we and have a lot of fun too :)</span>