Answer:
D 17 cm
Step-by-step explanation:
The Pythagorean theorem states
a^2 +b^2 = c^2
where a and b are the legs and c is the hypotenuse
4.2^2 + 16^2 = support ^2
17.64 +256 = support ^2
273.64 = support ^2
Take the square root of each side
sqrt(273.64) = sqrt(support ^2)
16.54206759 = support
The support is closest to 17 cm
