Why are liquids and gases categorised as fluids?

In water saturated air,the mole fraction of water vapour is $0.02$. If the total pressure of the saturated air is $1.2 \; atm$,the partial pressure of dry air is .....$atm$.

The rate of diffusion of $SO_2$ and $O_2$ are in the ratio:

$A$ gaseous mixture of $3$ gases $A$, $B$ and $C$ has a pressure of $10 \,atm$. The total number of moles is $10$. If the partial pressures of gases $A$ and $B$ are $3 \,atm$ and $1 \,atm$ respectively, and the molar mass of gas $C$ is $2 \,g/mol$, calculate the weight of $C$ in the mixture. (in $\,g$)

What will be the pressure at $0\,^oC$ in Kolkata,Chennai,and Mumbai (in $,bar$)?

At which of the following conditions is the density of a gas maximum?