<prompt> Which of the following OPV ls are usable?Only 1Only 1, 2Only 1, 2, 3Only 3, 4  <response>: Rules for VVM use in India Rules 1: If the inner square is lighter than the outer circle, the vaccine may be used Vials 1, 2 Rules 2: If the inner square is the color as, or darker than, the outer circle, the vaccine must not be used Vials 3, 4. 