After a Switch Is Thrown to Remove the Battery from a DC

Multiple Choice

After a switch is thrown to remove the battery from a DC LR circuit, but the circuit is still left complete, the time constant represents

A) the time rate of change of the current in the circuit.
B) the time rate of change of the induced emf in the circuit.
C) the magnitude of the ratio of the current to the time rate of change of the current.
D) all of the above.
E) only (a) and (b) above.