Translational motion of the rigid body is defined as one in which any line, say PQ, remains parallel to a fixed direction. Let $\overline{\mathrm{R}}_{\mathrm{A}}, \overline{\mathrm{R}}_{\mathrm{B}}, \overline{\mathrm{R}}_{\mathrm{p}}, \ldots \overline{\mathrm{v}}_{\mathrm{A}}, \overline{\mathrm{v}}_{\mathrm{B}}, \overline{\mathrm{v}}_{\mathrm{p}} \ldots$ and $\overline{\mathrm{a}}_{\mathrm{A}}, \overline{\mathrm{a}}_{\mathrm{B}}, \overline{\mathrm{a}}_{\mathrm{p}} \ldots$ denote the position vectors, velocity vectors and acceleration vectors
of $\mathrm{A}, \mathrm{B}, \mathrm{P} . .$ with respect to $\mathrm{O}$. Then, for translational motion.
(a) $\overline{\mathrm{R}}_{\mathrm{p}}-\overline{\mathrm{R}}_{\mathrm{A}}$ must be a constant vector
(b) $\overline{\mathrm{v}}_{\mathrm{A}}=\overline{\mathrm{v}}_{\mathrm{B}}=\overline{\mathrm{v}}_{\mathrm{p}}=\ldots$ and $\overline{\mathrm{a}}_{\mathrm{A}}=\overline{\mathrm{a}}_{\mathrm{B}}=\overline{\mathrm{a}}_{\mathrm{p}}=\ldots$ at any instant t.
(c) A, B, C, P, ... must move in straight lines that are parallel.
(d) All of the above.