Tech A says that hydraulic braking systems use proportioning valves and metering valves. Tech B says that hydraulic braking systems use pressure differential valves, or anti-lock hydraulic control units to modify hydraulic pressure. Who is correct?

A) Tech A
B) Tech B
C) Both Techs A and B
D) Neither Tech A nor B

Option C) Both Techs A and B

moving ball hits still ball. mover stops, hit ball moves. momentum transfer.

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.