An Inductor Produces a Back Emf in a DC Series

An inductor produces a back emf in a DC series RL circuit when a switch connecting the battery to the circuit is closed. We can explain this by

A) Lenz's law.
B) increasing magnetic flux within the coils of the inductor.
C) increasing current in the coils of the inductor.
D) all of the above.
E) only (a) and (c) above.