What is true about this reaction involving hydroxy carboxlic acid?
I think your guess for P is correct, we just don't know whether it is 2- or 3-hydroxy-butanoic acid.  Reaction of thionyl chloride with the hydroxyl group in the alkyl chain can proceed with retention or inversion of configuration depending on reaction conditions, but the point is, if P is optically active, then Q will be optically active too (so A seems correct).  Reaction of Q, an acid chloride, with ethyl amine will produce the corresponding ethyl amide, R.  Since amides are basic (they can form salts with acids), I think B and C are true too.  An optically inactive isomer of P would be 4-hydroxy-butanoic acid.  On heating it would dehydrate and form a stable lactone (S) that would not react with thionyl chloride, so I think D is true also.  I just wonder if we're missing something that would allow us to determine if P is the 2- or 3- isomer?

Update:  To be complete and accurate let's update.  Based on the comments below (particularly JA's) I was right about "B" (but for the wrong reason, I thought the amide would be basic enough, but it is not; B is true because, as JA points out, heating with excess amine will convert P into an amino amide (I've labeled it as X) which is basic).  I was wrong about C, R is not basic enough to form a salt.  I still don't know if P is 2- or 3-hydroxy-butanoic acid, but I've added a picture based on the 3-hydroxy isomer to try and summarize the chemistry.