As shown in the circuit, the circuit is in a steady state before the switch K is opened, and the switch K is turned on at t=0. The initial vlotage value of the inductance u(0+) is equal to ________.Choose A,B,C or D. Before the switch K is opened, the circuit has been in the steady state, the ideal wire make the branch of the inductance and the 10Ω resistor shorted. The current flows through the inductance is 0. So when the switch K is opened, the inductance can be treated a current source of 0 A current, the equivalent circuit is an open circuit in the place of the inductance. So only the resistor of 20 Ω has 2 A current. The voltage of the two terminals of the inductance is equal to the voltage of the resistor of 20 Ω.