How does poor flexibility cause low back pain?

Although not fully understood, low back pain problems are usually linked to two areas: 1) lifestyle, which includes stress, lack of exercise and poor posture, and 2) physical injury or disease. Stress can be a precursor to low back pain by upsetting your nervous system, causing your muscles to go into spasm.

Explanation:

answer(b) keep oxygenated and deoxygenated blood separate;