Was 70 the average grade on a class test?
A. On the test, half of the class had grades below 70 and half of the class had grades above 70.
B. The lowest grade on the test was 45 and the highest grade on the test was 95.

A) : Let us assume there are two students in the class, scores of each are 68 and 73 respectively. (Since, half scored less than 70 and half more than 70)

Now, average is not equal to 70, but if each scored 68 and 72, then the average will be 70.

Since, marks are not given, hence this statement alone is not sufficient.

B) : Similarly this statement alone is also not sufficient, as marks of rest of the students are not given.

Even by combining both statements, we wont be able to find the average.

=> Ans - (D)