Determining the product which is not possible in the reaction
@Pete
B1 is same as D1

But, D1 &amp; D2 are not same.

@Aniline
I see some problem in the options while it was framed/typed/published

I have shown the 6 possible stereoisomers, which have have labelled independently as A, B, C, D, E &amp; F

For the sake of clarity have generated their names with some software [not from my own] to be assured that these are actually different or same compounds.

Showing the mechanism, how there is a possibility of getting SIX by a free radical mechanism:



This one a redraw of the options A, B, C &amp; D with their names:


The relationship of D1 &amp; D2 as per question doesn't work to the the same:

In my opinion, there are six stereoisomers possible, but the correct option does not exist, in the question[options given, in fact].

Hope it throws some more light on your query.