The motion of a piston inside a cylinder is-

Correct answer: d i, ii and iii

All the piston's particles move together the same way (translational), the same motion returns after equal intervals (periodic), and it goes to and fro between two ends (oscillatory).

Why the other options are wrong

• a i and ii: It leaves out iii: the piston goes back and forth between two ends, so it is oscillatory too. All three are true.
• b ii and iii: It leaves out i: the piston does not turn, and all its particles move the same distance the same way at the same time, so it is translational too. All three are true.
• c i and iii: It leaves out ii: each to-and-fro takes the same time, so the motion is periodic too. All three are true.