which of the following statements is true? a.) in a standard normal distribution, the mean is equal to 1 and the standard deviation is equal to 1. b.) in a standard normal distribution, the mean is equal to 1 and the standard deviation is equal to 2. c.) in a standard normal distribution, the mean is equal to 0 and the standard deviation is equal to 1. d.) in a standard normal distribution, the mean is equal to 0 and the standard deviation is equal to 2.
