The Normal Lapse Rate is the average rate at which air temperature decreases with increasing altitude in the troposphere. The standard value is approximately 6.5°C for every 1,000 meters (or 3.6°F per 1,000 feet). This rate is used by scientists as a benchmark for atmospheric stability and for calibrating aircraft altimeters. ANSWER: (C) 6.5°C per 1,000 meters