The motion along a straight line is called as:
Linear
Explanation for the correct option
(D): Linear
Linear Motion
Linear motion is defined as a straight-line motion. Here, the body travels linearly, i.e. straight line.
Explanation for the incorrect options
(A): Vibratory motion is a to and from motion.
(B): Stationary motion is an object at rest.
(C): Circular motion is a motion of an object in a circular path.
Therefore, the motion along a straight line is called linear motion.
Hence, Option (D) is the correct answer.