The number of water molecules present in a drop of water (volume 0.0018 ml) at room temperature is

Question

$\begin{array}{1 1} a.1.568 \times 10^3 \\ b. 6.023 \times 10^{19} \\ c. 4.84 \times 10^{17} \\ d. 6.023 \times 10^{23} \end{array}$