Answer:
A. The melting of ice is both a desirable and undesirable change because, ice is needed to melt so as to make liquid water available for animal and plant use and consumption and also to release the energy used in the fusion process of ice formation. Melting of ice is undesirable because melting ice liberate water slowly, and the water liberated can erode surface soil. Melting ice reduces the available heat sink on earth and also reduces the available stored up fresh water supply on earth.
B. The appearance of hailey comet once every 72 year is a periodic change because it's motion around the solar system is repeated with time. The reason for this highly elliptical and eccentric path of motion is largely due to the gravitational effect of the sun and the planets on the comet.
Answer:
d) 0 V
Explanation:
It can be showed that the potential due to a point charge q, to a distance d from the charge, can be expressed as follows:

where k = 
As the potential is an scalar, and is linear with the charge, we can apply the superposition principle, which means that we can find the potential due to one of the charges, as if the other were not present.
By symmetry, all four charges are at the same distance from the center, so we can write the total potential, as follows:

where d, is the semi-diagonal of the square, that we can find applying Pythagorean theorem, as follows:

Replacing by the values in (1) we have:

which is equal to the option d).
Cp shows the amount of energy needed to raise temperature by one degree for one gram of water.
Formula for calculating cp is:

Final temperature is 26.73°C.
<span>The answers are:
bulb, motor, buzzer and swtich.As seen in the picture attached,
The electric current leaves the battery passes through
the bulb. It then travels through the
motor, next through the
buzzer and finally passes through the
switch before returning to the battery.</span>
Answer:
I think B) is uncorrect
Explanation:
As A) p=w/t so it's correct relation
C) power depend on time and work as work is distance multiple force so it refer to velocity
D) the powerful mean much work in a few time