Jones is a personal trainer at the local gym.

Mr. Jones is a personal trainer at the local gym. His newest client has come to him for help in developing her abdominal muscles. Mr. Jones decides that his client should perform leg lifts (pictured below), crunches, and full sit-ups. Considering how hip flexion affects exercises targeting the abdominal muscles, which of these exercises is likely to be the most appropriate for developing abdominal strength? How could Mr. Jones' client best work her abdominal muscles and minimize action of her hip flexors?

Pictured here is Mr. Jones' client performing leg lifts. Notice her finishing position in picture C.