Need for Nomenclature

Q. The common name of the group $(C{H}_3{)}_{3}CC{H}_{2}C{H}_2-$ is:

1. Isobutyl
2. n-Hexyl
3. Neohexyl
4. Neopentyl

Q. The common name of the group $(C{H}_3{)}_{3}CC{H}_{2}C{H}_2-$ is:

1. Isobutyl
2. n-Hexyl
3. Neohexyl
4. Neopentyl