This may seem a bit confusing at first, but there's a way to get it right every time. If you find "who," "which," or "that" introducing a dependent clause (like in the examples above):

1. Look at the word right in front of it (usually that's the word it takes the place of).

2. Decide if the word is singular or plural (that will tell you whether "who," "which," or "that" is singular or plural).

3. Make the verb agree!

That's all there is to it!

5. Closing down by doing a quiz

To end the period you are going to take a quiz on subject-verb agreement.