The correct answer is A. stop.
When the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will stop. This is because the motor will no longer have a magnetic field to turn the rotor. The rotor will simply sit there and not rotate.
Option B is incorrect because the motor will not run as an induction motor. An induction motor requires a rotating magnetic field to induce current in the rotor. Without a magnetic field, the rotor will not have any current flowing through it and will not rotate.
Option C is incorrect because the motor will not function as a static condenser. A static condenser is a device that stores electrical energy in an electric field. The motor does not have an electric field, so it cannot store electrical energy.
Option D is incorrect because the motor will not burn with dense smoke. The motor will simply stop rotating. There is no reason for it to burn or produce smoke.