1. Correct Answer: Option C: Two
 2. Explanation:
     To solve this problem, we need to arrange the letters of the word "INCOMPREHENSIBILITIES" in reverse alphabetical order and then determine how many letters remain in their original positions.
     Step-by-step Solution:
     ● Original Word: INCOMPREHENSIBILITIES  
     ● Reverse Alphabetical Order:  
           ○ First, list the letters in alphabetical order: B, C, E, E, E, H, I, I, I, I, L, M, N, N, O, P, R, S, S, T.
           ○ Then, reverse this order: T, S, S, R, P, O, N, N, M, L, I, I, I, I, H, E, E, E, C, B.
     ● Compare Positions:  
           ○ Original: I, N, C, O, M, P, R, E, H, E, N, S, I, B, I, L, I, T, I, E, S
           ○ Reversed: T, S, S, R, P, O, N, N, M, L, I, I, I, I, H, E, E, E, C, B
     ● Unchanged Positions:  
           ○ The letter 'I' at the 9th position in the original word remains in the same position in the reversed order.
           ○ The letter 'I' at the 15th position in the original word remains in the same position in the reversed order.
     Therefore, there are two positions where the letters remain unchanged.
     Hence, the correct answer is Option C: Two.