Final answer:
The discussion is centered on a particle moving along the x-axis with constant speed, which implies a lack of acceleration if velocity is constant. However, the position of the particle does change over time, corresponding to the linear motion. This concept is fundamental in understanding the principles of physics regarding motion.
Step-by-step explanation:
The main concept of the student's question is a particle moving along the x-axis. We can address this concept through a physics perspective by discussing multiple aspects of linear motion with constant velocity. First, when an object is in linear motion with constant velocity, its speed is constant, which means a) yes, it does move in a straight line, b) no, its acceleration is not zero because it has a constant speed but zero acceleration only if velocity is constant, and d) yes, its position changes with time due to movement. The acceleration of a particle is defined by the rate of change in velocity over time. If the acceleration is zero, the velocity is unchanging, and the speed is constant. The position changes by the same amount over equal time intervals, indicative of a constant speed.