How can you identify an emergency vehicle?

• They use flashing red or blue lights.
• They use a siren bell.
• It is hard to identify them.
• Both A & B
  Explanation:

  "Emergency vehicles – police, fire, ambulance, and special public-utility vehicles – can be easily identified through their use of flashing red or blue lights, a siren or bell, or alternating flashes of white light from their headlamp high beams."