The time period t of a simple pendulum is given by the relation
t=2pi sq rt l/g
, where l is the length of the pendulum and g is the gravitational field at the place. from the above relation, we can say that:

t ∝ g

t ∝ l

t2 ∝ g

t2 ∝ l

grav potential energy

its c i just checked it

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.