Option 1, 4.84 x 10^17, is not the correct answer. This option suggests that there are 4.84 x 10^17 water molecules in the tiny drop of water, which is too low of a number.

Option 2, 4.184 x 10^18, is also not the correct answer. This option suggests that there are 4.184 x 10^18 water molecules in the tiny drop of water, which is still too low of a number.

The correct answer is option 3, 6.023 x 10^19. This option suggests that there are 6.023 x 10^19 water molecules in the tiny drop of water at room temperature. This number represents Avogadro`s constant, which is the number of units of a substance in one mole. In the case of water, one mole is equal to 18 grams, and each mole of water contains 6.023 x 10^23 water molecules. Since the volume of the drop is given as 0.0018 ml, the number of water molecules can be calculated by multiplying the volume by the density (which is approximately 1 g/ml) and dividing by the molar mass of water