Each box contains 10 items. B.
Box 1
Net mass A = 10 grams
Box 2
Net mass B = 5 grams
Box 3
Each made of 1 A and 1 B
Mass box A = 10 grams; Mass box B = 5 grams; Mass box C-made of one A and one B
Mass ratio A/B =

?

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 .

  super sorry but i dont know lo

Answer246 k;

A. is your answer.  hope this