A square has a side length of 15 cm. Which of the following is closest to the length of a diagonal of the square?

A. 15 cm
B. 18 cm
C. 21 cm
D. 24 cm

PLEASE HELP PLEASE

Which answer is it for it to be simplified completely?

How to choose the sign of the radical in the denominator of the formula for the distance from a point to a line.

Atriangle has an area of 72 square inches. if the base of the triangle has a length of 18 inches, what is the height of the triangle? use the formula for the area of a triangle: area = (base)(height) type a numerical answer in the space provided. do not include the units or spaces in your answer.