Paru moves on a straight road from point A to C. She takes 20 minutes to cover a certain distance AB and 30 minutes to cover the rest of the distance BC. She then turns back and takes 30 minutes to cover the distance CB and 20 minutes to cover the rest of the distance to her starting point. She makes five rounds on the road the same way. Paru concludes that her motion is

Question

$\begin{array}{1 1} \text{a. Only rectilinear motion} \\ \text{ b. Only periodic motion} \\ \text{ c. Rectiinear and periodic motion} \\ \text{ d. Neither rectilinear nor periodic motion} Answer: c \end{array}$