About 39/50 of earth's atmosphere is made up of nitrogen. about what percent of the atmosphere is not nitrogen

When turned about its axis of rotation, which shape could have created this three-dimensional object?

The parabola y = x² - 4 opens: a.) up b.) down c.) right d.) left

Abicycle training wheel has a radius of 3 inches. the bicycle wheel has a radius of 10 inches.approximately how much smaller, in square inches and rounded to the nearest hundredth, is the area of the training wheel than the area of the regular wheel? *