This type of suspension has an upper and lower control arm that attaches to the steering knuckle by a ball joint. Opposite points will go to the frame.

• A. MacPherson Strut
• B. Double Wishbone
• C. Trailing Arm Suspension
• D. Short/Long Arm Suspension (SLA)

Answer: (D)

Two-arm independent front suspension with unequal arms, known as Short/Long Arm (SLA), uses a short upper control arm and a longer lower control arm. Both arms connect to the steering knuckle with ball joints, while their opposite ends mount to the frame. This arrangement matches the description: there are both an upper and a lower arm that meet the knuckle via ball joints, and the other ends are attached to the frame, allowing vertical wheel motion without a solid axle. The MacPherson strut system relies on a single lower arm plus a strut rather than two arms to the knuckle. A trailing arm setup uses a different geometry with the arm typically extending rearward, not a two-arm to the knuckle configuration. A double wishbone also uses two arms to the knuckle, but the defining feature here is the unequal-length upper and lower arms of the SLA design.