By "between the lower and upper quartiles" it means Michael scored in the middle 50%, however 64-76 represents the middle 68%, therefore his actual range is a little smaller, thus A
I think I got it now. The lower quartile is referring to 25% (as in Q1 from box plot) and the upper quartile is referring to 75%(Q3). As Imaiyuki mentioned 1 standard deviation within the mean is approximately 68% of the data.
Divide by 2 => 34% of data is above the mean and 34% below the mean. 34-25 = 9. So 1 standard deviation encompasses 9% more of the population on each side of the quartile.