Final answer:
The alkyl group in CH(CH3)CH(CH3)2 is a tertiary alkyl group.
Step-by-step explanation:
The alkyl group in CH(CH3)CH(CH3)2 is a tertiary alkyl group. It is classified as tertiary because the carbon atom to which the CH3 groups are attached is connected to three other carbon atoms. Therefore, the answer is B) Tertiary alkyl group.