Definition: In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D". 
Input: [header] How to replace ball joints [title] Prep the work area. [step] Park on a flat surface and block both rear wheels, front and back. Jack both front wheels off the ground and support the vehicle with jack stands. <sep> (A) Chock the back tires to make sure nothing will move anywhere while you're working. [title] Inspect the ball joints to make sure they need to be replaced. (B) [substeps] Using jack stands will give you greater stability as the vehicle will continue to move forward under pressure. It will also put less pressure on any place except the rear wheels and the floor mats. (C) If necessary, purchase a jack stand or at least some other attachment. [title] Install ball joints with a heavy saw. (D) [title] Mark the area where you do not want the surface to be cleaned. [step] Use gutter liners to mark the area you want to use to be cleaned up using gutter liners.
Output:
A