B. Mouthguards are needed to play hockey
The answer is D because everyone benefits from physical activity.
The circulatory system delivers oxygen and nutrients to cells and takes away wastes.
Answer:
How Does It Work? Most birth control pills are "combination pills" containing a mix of the hormones estrogen and progesterone to prevent ovulation (the release of an egg during the monthly cycle). A woman cannot get pregnant if she doesn't ovulate because there is no egg to be fertilized. The answer is D.
