The heights of a certain type of tree are approximately normally distributed with a mean height Mu = 5 ft and a standard deviation Sigma = 0. 4 ft. Which statement must be true? A tree with a height of 5. 4 ft is 1 standard deviation below the mean. A tree with a height of 4. 6 ft is 1 standard deviation above the mean. A tree with a height of 5. 8 ft is 2. 5 standard deviations above the mean. A tree with a height of 6. 2 ft is 3 standard deviations above the mean.