Write the next sentence in the following story.

How to keep your posture straight when you carry a heavy backpack
Wear the backpack as it was designed to be worn.
Namely, wear it on your back, with all parts doing what they're supposed to do.
Wear both straps.
Place a strap over each arm so that the straps sit evenly across each shoulder. Wearing the bag on only one shoulder causes strain and will make your posture lopsided.