Aline on a typical speed vs. time graph means an object is experiencing a constant acceleration.
a.) curved upward
b.) curved downward
c.) slanted upward to the right
d.) slanted downward to the right

The answer should be C. slanted upward to the right.

Hope this helps. :-)

d is the correct 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.