Final answer:
The most stable radical among the options given would be the one with the most electron delocalization, which is a tertiary radical center.
Step-by-step explanation:
A stable radical is one that has an unpaired electron in a partially filled orbital. In general, a radical with more electron delocalization or resonance is more stable. Among the options given, the most stable radical would be the one with the most electron delocalization.
For example, if we consider the radical A, it has a primary radical center. This means that the unpaired electron is on a carbon atom with one alkyl group attached to it. On the other hand, radical E has a tertiary radical center, with the unpaired electron on a carbon atom with three alkyl groups attached to it. Since tertiary radicals are more stable than primary radicals, radical E would be the most stable.