English Has Many Grammatical Rules

I think it of great importance to use correct subject verb agreement/pronoun antecedent agreement. Yes, it's one of the rules of grammar not as strictly followed as some of the others, but I find it annoying all the same when used incorrectly. Maybe it's from my sixth grade English teacher hammering my class with these rules. I don't know. Anyway, if any of you here aren't sure what I mean by "subject verb agreement/pronoun antecedent agreement," I shall demonstrate.

Subject verb agreement:

Correct-"What were you doing?"

Incorrect-"What was you doing?"

Pronoun antecedent agreement:

Correct-"I heard someone call my name, and his or her accent sounded British."

Incorrect-"I heard someone call my name, and their accent sounded British."

Now, let's put what we've learned into practice, shall we?