Body temperature varies over a 24-hour period, with a low point roughly between 4 a. m. and 5 a. m. Speed of reaction varies in line with body temperature, such that whenever body temperature is low, speed of reaction is low. If low body temperature caused slow reaction, the speed of reaction should increase if we artificially raised body temperature during the period 4 a. m. to 5 a. m. But the speed of reaction does not increase. Which one of the following conclusions can properly be drawn from the above statements? ['Low speeds of reaction do not cause low body temperature.', 'Low body temperatures cause low speeds of reaction.', 'Low body temperatures do not cause low speeds of reaction.', 'Low speeds of reaction cause low body temperature.']