3. What is the main difference between a physical change and a chemical change?
A. Physical changes alter the composition whereas chemical changes alter the
appearance of a substance.
B. Physical changes describe the appearance of a substance whereas chemical
changes describe qualities only observed with a reaction.
C. Physical changes describe qualities only observed with a reaction whereas
chemical changes describe the appearance of a substance.
D. Physical changes alter the appearance whereas chemical changes alter the
composition of a substance,

B and D could both be right as they are quit similar.

Consider two rods of the same length and diameter,

Increasing the diameter of one would change the expansion qualities of that rod even though there would be no chemical changes,

However, leaving the physical appearance of both rods the same while applying a reactive substance (acid or something) to one of the rods would not necessarily change the physical appearance of that rod but could make a considerable change in the  physical properties of that rod.

what was the answer?

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.