If infrared waves can move information through air, what is the advantage of sending their signals through networks of cables? 
A.
Cables are easy to maintain.

B.
Cables transmit infrared waves over longer distances.

C.
The denser the medium, the faster the wave.

D.
These waves need to travel only short distances.

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 .

The size is 8inches if ur a girl

The second and last option are the answers