Answer: B
D makes no sense because energy is created so we can remove that. C also makes no sense because if energy is not created how did it get destroyed if there's no energy in the first place. This leaves us with a and B the correct answer is B because energy is created and cannot be destroyed.
Oscillation is a type of periodic motion which repeats itself to and from about a point which is called mean position. The period of a Pendulum can be described as a ratio between the length and gravity as,

Here,
L = length
g = Gravity
If we rearrange to find the length we have that,

Our period is 2s and the gravity is 9.8m/s^2, then,


The simple required length of the pendulum must be 0.9929m
Answer:
An Ocean beach
Explanation:
a Ocean beach is far heavier than the top of a mountain, despite that a mountain is made with many heavy rocks a Ocean beach may have light sand but the layers of sand and the width would be way heavier then the top of a mountain.