10 salt water is classified as a
(1) compound because the proportion or its atoms is fixed
(2) compound because the proportion of its atoms can vary
(3) mixture because the proportion of its components is fixed
(4) mixture because the proportion of its components can vary

Compound would imply that the salt and water were chemically bonded together, which they aren't

As there is no specific amount of salt required for water to be deemed salinated, the answer would be 4

Coal i believe hope this

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .