Dr. Laura Bohn has made a career out of studying how opioids affect the brain. Her research focuses on how to make painkillers safer and non-addictive. NFEPP is a synthetic opioid similar to morphine, but it can bind to opioid receptors only under acidic conditions (as in inflamed and therefore painful tissue injuries) but not in the brain or elsewhere in the body. The influx of white blood cells during the inflammatory response increases glucose and oxygen demand. Lactic acid secretion by the inflammatory cells changes the pH. Which of the following pH values may most closely approximate the pH of inflamed tissue?

a. рн7

b. pH 8 c. pH 4 d. pH 10