What is a sequence of transformations ?

When two or more transformations are combined to form a new transformation, the result is called a sequence of transformations, or a composition of transformations. ... When working with composition of transformations, it was seen that the order in which the transformations were applied often changed the outcome.

your answer is the last one

step-by-step explanation:

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