i just took the test, the correct answer is .. 31.5 in.
your answer is the last one
divide the length of a'c' by the length of ac to get a scale factor of two
& then reflect vertically (over the y-axis)
so your answer is dilation by a scale factor of 2 followed by reflection over the y-axis
C sqrt(45) is irrational
So C sqrt(45) is the answer
Hope this helped. Have a great day!