Which phrase describes a compound that consists of two elements? (1) a mixture in which the elements are in a variable proportion (2) a mixture in which the elements are in a fixed proportion (3) a substance in which the elements are chemically combined in a variable proportion (4) a substance in which the elements are chemically combined in a fixed proportion

Option D

Explanation:

Compound is made of more than one type of elements that is chemically combined in a fixed proportion.

Compounds are made of more than one type of elements. The elements of the compound are hold together by chemical bonds.

Two same elements does not forms any bond in the compound so different elements are required to form a bond.

hence, the correct answer is option D

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.

increased stability in the completion of fluorine's outer shell.