Identify the angle relationship pair and find the measures of angle I will give brainless for right answers

Which statement best describes a square? a. a special rectangle that has four right angles b. a special trapezoid that has four sides of equal length c. a special rectangle that has four sides of equal length d. a special trapezoid that has four right angles

What is the standard deviation of the following data set rounded to the nearest tenth? 3, 17, 18, 15, 12, 21, 9

You can find the constant of proportionality by finding the ratio of