To find the probability of drawing a vowel from the word "HIPPOPOTAMUS," follow these steps:

1. Count the total number of letters:
- The word "HIPPOPOTAMUS" has 12 letters.

2. Identify the vowels in the word:
- The vowels are I, O, O, A, U.
- Count the vowels: I (1), O (2), A (1), U (1).
- Total vowels = 5.

3. Calculate the probability:
- Probability = (Number of favorable outcomes) / (Total number of outcomes)
- Probability = Number of vowels / Total letters
- Probability = 5 / 12

So, the probability of drawing a vowel from the box is \(\frac{5}{12}\).

The correct answer is A. 5/12.