Hailey did 10 sets of sprints. when she relaxed afterward, her muscles started to feel sore. which of the following best explains what was built up in her muscles? energy from cellular respiration lactic acid from anaerobic respiration alcohol from fermentation carbon dioxide from cellular respiration

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.