Option C: 7
To solve this problem, we need to determine the number of different combinations of two subjects that can be chosen from the given five subjects, considering the condition that Mathematics II can only be chosen if Mathematics I is also chosen.
     Let's list the subjects:
         ○ Commerce (C)
         ○ Economics (E)
         ○ Statistics (S)
         ○ Mathematics I (M1)
         ○ Mathematics II (M2)
     Step-by-step Analysis:
     1. Identify all possible pairs without restrictions:
            ○ (C, E)
            ○ (C, S)
            ○ (C, M1)
            ○ (C, M2)
            ○ (E, S)
            ○ (E, M1)
            ○ (E, M2)
            ○ (S, M1)
            ○ (S, M2)
            ○ (M1, M2)
     2. Apply the restriction:
            ○ Mathematics II (M2) can only be chosen if Mathematics I (M1) is also chosen. Therefore, any pair that includes M2 must also include M1. This means the pairs (C, M2), (E, M2), and (S, M2) are not valid because they do not include M1.
     3. List valid combinations:
            ○ (C, E)
            ○ (C, S)
            ○ (C, M1)
            ○ (E, S)
            ○ (E, M1)
            ○ (S, M1)
            ○ (M1, M2)
     Conclusion: There are 7 valid combinations of two subjects that can be chosen, considering the restriction on Mathematics II. Therefore, the correct answer is Option C: 7.