Final answer:
At initial contact, the degree of hip flexion is 0 degrees. As the leg swings forward, the hip joint gradually starts to flex.
Step-by-step explanation:
The correct answer is A) 0 degrees.
At initial contact, the degree of hip flexion is 0 degrees. When someone takes a step and their foot touches the ground, the hip joint is in a fully extended position, meaning it is straight and not bent. As the leg swings forward and the heel comes off the ground, the hip joint starts to flex, allowing the knee to come up towards the chest.
For example, imagine a person walking and taking a step forward: when their foot contacts the ground, the hip joint is not flexed at all, and the leg is straight. As they continue to walk and swing the leg forward, the hip joint starts to bend, and the knee rises towards the chest.