When was Halley's comet last seen?

The Halley's comet appears after every

Categorize the motion as periodic or oscillatory motion (i) Motion of Halley 's comet around the sun (ii) Motion osf the penedulum of a wall clock (iii) Motion of liquid n a U-tube when liquid is once compresed in one limb and then left to itself Hint : In oscallatory motion, there is to and fro motion about some mean position.

What is the periodicity of Halley's comet?

State whether the following statements are true or false: Appearance of Halley's Comet once in every 76 years is a periodic change.