Ans- Air is a heterogeneous mixture. Beacuse Air is a mixture multiple gases and elements.
for more information :
Homogeneous mixture:-
A homogeneous mixture is contain of one compound or one element of similar kind.
For example: water, common salt, cooking oil, milk, etc.
Heterogeneous mixtures:-
A heterogeneous mixture is the combination of two or more compounds or element of different kind.
For example: air,mixture of sand & water, a mixture of oil & water, etc.