IUPAC name of the following compound is

2-Cyclohexylbutane
2-Phenylbutane
3-Cyclohexylbutane
3-Phenylbutane

Here, the main chain is butane and the position of phenyl will be decided by the lowest locant rule. (Here it is 2)
So,the IUPAC name is 2-Phenylbutane
Therefore, option (2) is correct.