28. physical fitness can be broken down into four health-related parts – cardiorespiratory endurance, muscular strength and endurance, flexibility, and body composition. the following relates to muscular endurance: a. the ability of your heart, blood vessels, and lungs to distribute nutrients and oxygen and to remove wastes. b. the ability of muscles to keep working for an extended period of time. c. the ability to use a muscle throughout its entire range of motion. d. is the amount of body fat compared to lean tissue, such as muscle and bone.

[120 total points] (public health) in one of the largest human experiments ever conducted, in 1954 a randomized controlled trial was run to see whether a vaccine developed by a doctor named jonas salk was effective in preventing paralytic polio. a total of 401,974 children (ages 6–9), chosen to be representative of those who might be susceptible to the disease, were randomized to two groups: 200,745 children (the control group c) were injected with a harmless saline solution (a placebo) and the other 201,229 children (the treatment group t) were injected with salk’s vaccine. what was the point of giving saline solution to the children who didn’t get the vaccine? explain briefly.