For a simple harmonic motion energy is given with:

Where k is a constant that depends on the type of the wave you are looking at and A is amplitude.
Let's calculate the energy of the wave using two different amplitudes given in the problem:

We can see that energy associated with the wave is 4 times smaller when we decrease its amplitude by half. So the answer should be C.
<span>In a
real machine, the work output is always less than the work input is true. The answer
is letter A. it follows the law of entropy where no energy can be converted completely
into work. Under this law, Carnot’s theorem states that Carnot’s engine can
perform 100% of work. However, no such engine has ever succeeded the conversion
of work into 100%. The greatest efficiency so far is at 80%. Because there will always be factors that
could affect the conversion of work. </span>
Is there suppose to be an image?