The very high voltage needed to create a spark across the spark plug is produced at the a. transformer's primary winding. b. transformer's secondary winding. c. battery. d. breaker points.

b ) transformer's secondary winding.

Explanation:

When we switch on the car , the breaker point is closed sending current through primary winding of a transformer creating magnetic field in it. When the point is  opened again  , current stops in the primary coil ,reducing magnetic field to zero. This creates very high voltage in the secondary winding . 12 volt of car battery is transformed into 30000 volt in secondary coil. This high voltage is carried to spark plug by high tension wire.

its c i just checked it