While traveling on a frontage road of a controlled-access highway, you must yield the right-of-way to a vehicle:

• Entering or about to enter the frontage road from the highway
• Leaving or about to leave the frontage road to enter the highway
• Already travelling on the frontage road
• Both A & B
  Explanation:

  "The driver traveling on a frontage road of a controlled-access highway must yield the right-of-way to a vehicle entering or about to enter the frontage road from the highway; and leaving or about to leave the frontage road to enter the highway."