Correct Option: B

There are different methods of counting microbial growth. These are based on different parameters of cells such as dry-weight and wet-weight measurement, absorbance, cell plate, density, turbidity, ATP measurement, viable count, ATPase activity and use of Coulter counter. Absorbance is measured by using a spectrophotometer. Cell growth of any bacterial suspension at a particular wavelength at different intervals is measured in terms of absorbance.