IUPAC name of propiophenone is:

1-Phenylpropan-1-one

The correct answer is option 2. 1-Phenylpropan-1-one. 

The correct IUPAC name for propiophenone is 1-Phenylpropan-1-one.

In this compound, the parent chain consists of three carbon atoms (propan-). The ketone functional group (C=O) is on the first carbon of this chain. There is a phenyl group attached to the second carbon of the parent chain.

Therefore, the correct name is 1-phenylpropan-1-one, indicating the position of the ketone group and the substituent.