Which of the following is a secondary radical :-A Isobutyl B Isopropyl C Ter butyl D Neo pentyl

The answer is B, Isopropyl.

Here's why:

A secondary (2°) radical is an alkyl radical in which the carbon atom that carries the unpaired electron is bonded to two other carbon atoms.

A. Isobutyl is a primary (1°) radical because the carbon atom that carries the unpaired electron is bonded to only one other carbon atom. B. Isopropyl is a secondary (2°) radical because the carbon atom that carries the unpaired electron is bonded to two other carbon atoms. C. Tert-butyl is a tertiary (3°) radical because the carbon atom that carries the unpaired electron is bonded to three other carbon atoms. D. Neo pentyl is also a tertiary (3°) radical because the carbon atom that carries the unpaired electron is bonded to three other carbon atoms.