There are some points on a standing
wave that never move. what are
these points called?
a. harmonics
b. normal modes
c. nodes
d. anti-nodes
e. interference

Nodes.

Explanation:

Nodes are a point that are on a standing wave that never move.

C. Nodes

Explanation:

There are some points on a standing  wave that never move. These points are called Nodes.

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.