Consider U = (x\x is a negative real number). Which is an empty set?
O fx]xEU andx has a negative cube root}
O fx]xEU andx has a negative square root}
O x]xEU and x is equal to the product of a positive number and-1}
O x]xEU and x is equal to the sum of one negative and one positive number}

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.

i don't understand. explain it clearly

answer///scientific method;