The answer is A. Validate emotions
In active listening, the listener is mindful of what is being said. Not only he/she is listening to every word, but also processing the information and offering feedback. The purpose of active listening is to understand what the speaker is saying completely, in a non-judgmental way. It involves focusing on facts and feelings. There is a set of principles to do it efficiently: encourage, question, restate, reflect, summarize, and validate.
The sentence “I don’t know why you’re angry, it’s not like I was trying to upset you” violates the principle of validating emotions. The person who says it does the precise opposite by rejecting the speaker’s feelings and avoiding the chance to understand them.