Answer:
Option D
Step-by-step explanation:
Given : Christina is randomly choosing 3 movies to take on vacation from 9 action movies, seven science fiction movies, and four comedies.
To find : Which statement is true?
Solution :
Total number of movies 9 + 7 + 4 = 20
The total number of combinations of choosing 3 movies from a pool of 20 is represented by 
Since there are 9 action movies in total and we're choosing 3, the number of combinations to do that is 
So the probability of choosing all action movies is the combinations of choosing all action movies divided by all the possible combinations of choosing any 3 movies from 20.

Therefore, the probability of not choosing all action movies is

Hence, Option D is correct.