Count every stereoisomer (enantiomers counted separately) as a different product. The total number of monochlorination products that can be formed by free radical chlorination of 3-methylpentane is

3-Methylpentane has four kinds of H and gives four constitutional products. 1-Chloro-3-methylpentane has one stereocentre (C3): 2 stereoisomers. 2-Chloro-3-methylpentane has two stereocentres (C2, C3): 4 stereoisomers. 3-Chloro-3-methylpentane is achiral: 1. 1-Chloro-2-ethylbutane is achiral: 1. The total is $2+4+1+1=8$.