What must you remember when coupling up a trailer?

You answered correctly. When coupling up a trailer, it's important to release both the parking brake and remove the wheel chocks once the trailer is securely attached. Additionally, you should not connect coupling parts that have different colors because the color system helps to ensure that the right connections are made safely. This prevents incorrect coupling and possible safety hazards. Always match colors when connecting coupling parts and only release the parking brake and wheel chocks after the trailer is coupled to avoid rolling. Understanding and following these rules helps prevent accidents and ensures safe trailer operation.