Correct Answer - C
In the given circuit diode `D_1` is forward biased and `D_2` is reverse biased. The resistance of `D_1` is zero and that of `D_2` is infinite as the diodes `D_1` and `D_2` are ideal. No current flows through `D_2`.
Thus `D_1` can be replaced by a resistanceless wire and `D_2` can be replaced by a broken wire. The equivalent circuit is shown in the figure.
The current in the circuit is `I=(12V)/(4Omega+3Omega)=(12V)/(7Omega)=1.71 A`