17, a compound is a substance composed of two or
more elements that are
(1) chemically combined in a fixed proportion
(2) chemically combined in a variable proportion
(3) physically mixed in a variable proportion
((4) physically mixed in a fixed proportion

A

Explanation:

Compounds are chemically combined in a fixed proportion . Like Hydrogen and Oxygen together form H2O, it is in fixed proportion 2 Hydrogen for one Oxygen. Also, they are chemically combined thus water has different properties than the individual elements that make it.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).