What is a passing lane?

• A passing lane is a lane added for handicapped drivers, often in the mountains.
• A passing lane is a lane added to a highway to allow passing, often in the plains.
• Both A and B.
• A passing lane is a lane added to a highway to allow passing, often in the mountains.
  Explanation:

  "A passing lane is a lane added to a highway to allow passing, often in the mountains."