The raincoats are made waterproof by coating them with a material,which ............

The wettability of a surface by a liquid depends primarily on

Given below are two statements: One is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: Clothes containing oil or grease stains cannot be cleaned by water wash.
Reason $(R)$: Because the angle of contact between the oil/grease and water is obtuse.
In the light of the above statements,choose the correct answer from the options given below.

When the temperature is increased,the angle of contact of a liquid:

If $S_1, S_2$ and $S_3$ are the tensions at the liquid-air,solid-air,and solid-liquid interfaces respectively,and $\theta$ is the angle of contact at the solid-liquid interface,then:

$A$ capillary tube is dipped vertically in a liquid. If the liquid surface is hemispherical,then the angle of contact $\theta$ is