The powder-based packet to purify water failed for a number of reasons including Select one: a. Rust b. Expense c. Sales personnel who marketed the water were not natives of the villages or urban neighborhoods where the water was needed impurities d. Contamination

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 .

Idon't know hope someone you