Step 1: Understanding the question.
The sentence is describing someone's anger, and we need to choose the correct preposition to complete the phrase. "Anger" is commonly expressed as "anger against" when referring to a specific target or entity.
Step 2: Analyzing the options.
(A) with: This is incorrect, as "anger with" is not typically used in this context.
(B) for: This is incorrect, as "anger for" is not a typical construction.
(C) against: This is correct, as "anger against" is commonly used to describe being angry at something or someone.
(D) a: This is incorrect, as "anger a" does not make sense in this context.
Step 3: Conclusion.
The correct answer is (C) against, as it accurately describes the target of the anger.