The following circuit has a voltage source $${V_s}$$ as shown in the graph. The current through the circuit is also shown

The element connected between $$' a '$$ and $$' b '$$ could be

The nature of feedback in the op-amp circuit shown is

The following circuit has $$R = 10k\Omega ,\,C = 10\mu F.$$ The input voltage is a sinusoidal at $$50HZ$$ with an $$RMS$$ values of $$10V.$$ Under ideal conditions, the current $${{\rm I}_S}$$ from the source is

An ideal op-amp circuit and its input waveform are shown in the figures. The $$o/p$$ wave form of this circuit will be