The correct answer is 'find out'.
Here's why:
* The sentence uses 'as soon as,' indicating a future event. 'As soon as' is followed by the present simple tense (find) to describe the condition, and the future simple tense (will get) to describe the result.
* 'Parents' is a plural noun, so the verb must be in the plural form (find).
Therefore, the complete and correct sentence is:
"As soon as my parents find out my results, they will get angry."
Correct answer: find out