



In option (1)
To Balance Bridge
$$ \frac{P}{Q} = \frac{R}{S} $$
Here
$$ P = 10 \ \Omega $$
$$ Q = 10 \ \Omega $$
$$ R = 15 \ \Omega $$
$$ S = 5 + R_{diode} $$
The diode can conduct and have resistance RD=10Ω because diode have dynamic resistance. In that case bridge will be balanced.