Wanting to study the effect of exercise on preventing the common cold, a researcher collects 500 test subjects and randomly assigns them to a treatment group instructed to exercise and a control group instructed to not exercise. He later records the number of colds for each group. This is an example of: Group of answer choices linear regression independence an observational study an experiment

256π units²   (answer b)

step-by-step explanation:

the formula for the surface area of a sphere of radius r

is             a = 4πr²

and so, if r = 8 units, then the surface area is:

a = 4π(8 units)² = 256π units²   (answer b)

-8/2y-8=5/y+4-7y+8/y^2-16

we move all terms to the left:

-8/2y-8-(5/y+4-7y+8/y^2-16)=0

we can not solve this equation

x= 3^y

step-by-step explanation:

the argument of alfred t. mahan, henry cabot lodge, and albert j. beveridge was the economically and mass production the the americans could not consume themselves. this led expansion to sell to other foreign nations for profits.

step-by-step explanation:

this is my explanation