When a data set is normally distributed, about how much of the data fall within one standard deviation....?

This is talking about the Empirical Rule which states that 68% of the data set falls within 1 standard deviation of the mean, and 95% of the data set falls within 2 standard deviations of the mean, and 99.7% of the data set falls within 3 standard deviations of the mean. so naturally the correct answer is A. 68%