A certain list of 300 test scores has an arithmetic mean of 74 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 choice from the following answers:
A) 75 and 80 B) 80 and 85 C) 74 and 74 D) 75 and 75 E) 70 and 80
Ans: C   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 74 and 74 are the most close numbers and they will increase the number of elements in the set without changing the median value.   74 and 74
<result>C</result>
A certain list of 300 test scores has an arithmetic mean of 74 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?