Omega-3 fatty acids are important because they
a. the body absorb calcium.
b. increase the stomach's ability to digest foods.
c. make the bones less brittle.
d. reduce the amount of hardened material that forms on artery walls.

Omega-3 fatty acids are important because they help reduce the amount of hardened material that forms on artery walls - d.

Omega-3 fatty acids are considered a good addition to any diet due to the fact how they affect cardiovascular health (in a positive way) as well as cognitive functioning. 

Why  do you think body composition focuses  on the  ratio  of  fatty tissue  to  other body tissue? why is  body composition not related  to  weight?

If it's a smaller child or infant, place one on the middle of the chest and on the child's back. (if it is a bigger child with enough room for two, place one on the upper right/your left of the chest, and one on the lower left/your right) the pads should never touch each other.