Read the article and select the best answer. Article: Many people think walking is a good way to exercise and many fat people are advised to lose weight by walking. In fact, you can do it everywhere. Here's how to prepare for walking: ^Find a pair of shoes. It is easy to find a pair of shoes, but what matters most is comfort. ^Check your shape. The following tips will help you stay comfortable and get the most out of your walk: * Stand up straight. Imagine a string pulling you up from the center of the top of your head. Let that string pull you up as straight as possible. Relax your shoulders. * Look ahead. Keep your neck straight and your head held high to avoid unnecessary strain to your neck and shoulders. If you have to look down to see where you're going, lower your eyes, not your head. * Move your arms. Bend your elbows and let your arms swing naturally at your sides. You'll burn up to 15 percent more calories by keeping your arms moving. ^Stay safe walking is one of the safest activities you can do. Still, it's wise to take a few precautions . * If you're walking at night, wear a piece of reflective clothing. * When the weather's warm, be sure to drink a tall glass of water before you set out and another when you return. * If your path is rough, protect your ankles. Wear a comfortable elastic bandage for support, and keep your eyes focused on the path. Question: The purpose of staying right walking form is _ . Options: A: to relax your shoulders and neck B: to keep your balance C: to keep safe during walking D: to make full use of walk
D