Final answer:
Einstein's first postulate of special relativity indicates that the laws of physics are consistent across all inertial frames of reference, which covers moving at constant velocity in any direction or being at rest relative to each other.
Step-by-step explanation:
The first postulate of special relativity, stated by Einstein, maintains that the laws of physics are the same in all inertial frames of reference. Inertial frames of reference are those in which an object either remains at rest or continues to move at a constant velocity, meaning not accelerating. Therefore, the correct answer to the student's question is that the laws of physics are the same in all frames of reference that are in motion relative to one another at constant velocity, regardless of whether they are at rest with respect to each other, moving forward or away from each other, or moving parallel to each other. This encompasses all of the options provided: (a) at rest with respect to one another, (b) moving forward or away from one another at constant velocity, and (c) moving parallel to one another at constant velocity, which effectively means (d) all of these. This is because, in each scenario described, the frames of reference mentioned are inertial.