In the circuit below, the light dependent resistor $(LDR)$ receives light from the $LED$. The $LDR$ has resistances of $5\;k\Omega$ and $500\;\Omega$ under dark and illuminated conditions,respectively. The $LED$ is $OFF$ at time $t<0$. At time $t=0s$, the switch $S_1$ is closed for $1\;ms$ and then kept open thereafter. Assuming zero propagation delay in the devices, the $LED$
- turns $ON$ when $S_1$ is closed and remains $ON$ after $S_1$ is opened
- turns $ON$ when $S_1$ is closed and turns $OFF$ after $S_1$ is opened
- turns $ON$ when $S_1$ is closed and toggles periodically from $ON$ to $OFF$ after $S_1$ is opened
- remains $OFF$ when $S_1$ is closed and continues to remain $OFF$ after $S_1$ is opened