Data Sufficiency

Since we know three values in List S, and we know the mean, and thus the sum, of all five values in List S, then if we're given a fourth value in list S, we can find the fifth missing value. So from Statement 1 alone, we know exactly what List S contains. Similarly, from Statement 2 alone, we know exactly what list T is. So of course using both Statements, we can answer any question about the two lists, because we know exactly what they are. But neither statement could be sufficient alone, because we need to know about the missing values in each set, and the answer is C.