Which of the following is a redox reaction?

The decreasing order of nucleophilicity among the following nucleophiles is:
$(I)$ $CH_3-COO^-$
$(II)$ $CH_3-O^-$
$(III)$ $CH_3-CH_2^-$
$(IV)$ $CH_3-SO_3^-$

An electrolytic cell contains a solution of $Ag_2SO_4$ and has platinum electrodes. $A$ current is passed until $1.6 \ g$ of $O_2$ has been liberated at the anode. The amount of silver deposited at the cathode would be ............. $g$.

The parabola with directrix $x+2y-1=0$ and focus $(1,0)$ is

Which of the following is correctly matched?

$A$ rectangular loop has a sliding connector $PQ$ of length $2\ m$ and resistance $10\ \Omega$. It is moving with a speed $5\ m/s$ as shown in the figure. The set-up is placed in a uniform magnetic field of $3\ T$ directed into the plane of the paper. Find the three currents $I_1$,$I_2$,and $I$.