In Millikan's oil drop experiment for the determination of the charge on the electron,the reason for using oil is:

When $10^{19}$ electrons are removed from a neutral metal plate through some process,the charge on it becomes . . . . . . .

The sure check for the presence of an electric charge is

$A$ $1$ paisa coin is made up of an $Al-Mg$ alloy and weighs $0.75\, g$. It has a square shape and its diagonal measures $17\, mm$. It is electrically neutral and contains equal amounts of positive and negative charges. Calculate the total amount of positive or negative charge in the coin.

We have three identical metallic spheres $A, B$ and $C$. $A$ is given a charge $Q$,and $B$ and $C$ are uncharged. The following processes of touching of two spheres are carried out in succession. Each process is carried out with sufficient time.
$(i)$ $A$ and $B$
$(ii)$ $B$ and $C$
$(iii)$ $C$ and $A$
$(iv)$ $A$ and $B$
$(v)$ $B$ and $C$
The final charges on the spheres are

Can you neglect the quantization of charge?