The correct answer is option 2: parabolic.

In a simple pendulum, the time period (T) is the time taken for one complete oscillation, and the length (L) is the distance from the point of suspension to the center of mass of the pendulum bob. The relationship between the time period and the length of a simple pendulum is given by the equation T = 2π√(L/g), where g is the acceleration due to gravity.

When we plot T against L, we get a parabolic graph. As the length of the pendulum increases, the time period also increases. However, the relationship is not linear, which eliminates option 1 (straight line passing through origin) as the correct choice. Additionally, the graph does not form a circle or any other shape, so option 3 (circle) is incorrect as well.

Therefore, the correct answer is option 2: parabolic.