Answer

A-PR ; B-Q ; C-s ; D-P

Explanation

In this case `Br_2` undergoes exclusively anti addition through bromonium on

Another stereoisomer trans – form gives meso product. All stereo specific reactions are essentially stereo selective.

cis + syn addition ` to` meso form
cis + anti addition ` to` +dl form

Two possibel carbocation inttermedials are formed

As `3^(@)` is more stable that.s why gives predominate product gegioselective .

Optically inactive no other stereoisomer it has trans-12, di bromopropene Propane produces exclusively one stereoisomer as the predominant product. Hence reaction is stercoseletive