A crane operator using an electromagnet can drop off a load of scrap iron by . A. Neither turning on or off, there is no way to turn off an electromagnet
B. Either turning on or turning off an electromagnet
C. Turning off an electric current
D. Turning on an electric current

b.transmitters send radio waves, and receivers capture radio waves.

scientific laws are the result of testing theories and proving them to be facts.

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.