A certain list of 301 test scores has an arithmetic mean of 75 and a standard deviation of d, where d is positive. Which of the following two test scores, when added to the list, must result in a list of 302 test scores with a standard deviation less than d? Choose the correct answer.
A) 75 and 80  B) 75 and 75  C) 70 and 75  D) 74 and 75  E) 70 and 80
Deviation means spreading of the numbers from one median point value..   as the set is already established and we need to add only two numbers, this means we can only add numbers which are closer to the median to reduce the deviation.   so 75 and 75 are the most close numbers and they will increase the number of elements in the set without changing the median value.   75 and 75
<result>B</result>
A certain list of 301 test scores has an arithmetic mean of 75 and a standard deviation of d, where d is positive. Which of the following two test scores, when added to the list, must result in a list of 302 test scores with a standard deviation less than d?