Option C: S1 and S2 together are sufficient to answer the Question, but neither S1 alone nor S2 alone is sufficient to answer the Question.
   ● Statement S1: R is greater than P as well as Q.  
           ○ From this statement alone, we know that R > P and R > Q. However, we do not have any information about how R compares to S. Therefore, S1 alone is not sufficient to determine which number is the largest.
     ● Statement S2: S is not the largest one.  
           ○ This statement alone tells us that S is not the largest, but it does not provide any information about the relative sizes of P, Q, and R. Therefore, S2 alone is not sufficient to determine which number is the largest.
     ● Combining S1 and S2:  
           ○ From S1, we know R > P and R > Q.
           ○ From S2, we know S is not the largest.
           ○ Combining these, we can conclude that R must be the largest because it is greater than both P and Q (from S1), and S cannot be the largest (from S2).
     Therefore, both statements together are sufficient to determine that R is the largest number, but neither statement alone is sufficient. Hence, the correct answer is Option C.