Explain the mechanism by which ac (alternating current) through the primary circuit of a transformer produces an alternating voltage and current in the secondary coil. then explain why this would or would not work with dc (nonalternating current) in the primary coil.

The right answer for the question that is being asked and shown above is that: "It takes a changing magnetic field to create an electric field. So if it was DC the magnetic field from the primary would be unchanging, and no voltage would be induced." 

The best answer is (a) which is universal law is in effect at all times. it is constantly at play in everything we do and governs our lives. it is also important to note that universal law applies to not only everything on earth, but everything in the universe as well, which is another reason why it is in effect at all times.