The correct answer is A. P, Q.
Newman projections are a way of representing the three-dimensional structure of a molecule by looking down a particular bond. In the case of meso-2,3-butanediol, there are two equivalent Newman projections that can be drawn, as shown in P and Q. In both projections, the two methyl groups are in front of the plane of the paper, and the two hydroxyl groups are behind the plane of the paper. The two projections are mirror images of each other, and therefore represent the same molecule.
The other options are incorrect because they do not represent the correct three-dimensional structure of meso-2,3-butanediol. In option B, the two methyl groups are not in front of the plane of the paper, and in option C, the two hydroxyl groups are not behind the plane of the paper. In option D, the two projections are not mirror images of each other.