The density of water is $1$ g/ml. The volume of water drop is $1.8$ ml. The number of molecules present in one water drop is:

The correct option is D $6.023\times {10}^{22}$
From density, it can be said that $1$ g of water has volume of $1$ ml.

Thus, $1.8$ ml of water has mass of $1.8$ g.

$1$ mole of water weighs $18$ g.

Thus, $1.8$ g of water corresponds to $0.1$ mole.

$1$ mole of water contains $6.023\times {10}^{23}$ molecules.

Hence, $0.1$ mole of water will contain $6.023\times {10}^{22}$ molecules.