$30.$ Graphical methods for estimating the number of stages in an absorption column are preferred when:

$-$ A$)$ The process involves complex chemical reactions.

$-$ B$)$ The equilibrium data is readily available and straightforward.

$-$ C$)$ Precise control over product purity is not required.

$-$ D$)$ The solvent has a high viscosity.

$31.$ The Height Equivalent to a Theoretical Plate $($HETP$)$ impacts column design by:

$-$ A$)$ Allowing for the calculation of the minimum solvent flow rate.

$-$ B$)$ Providing a measure of the packing material's efficiency.

$-$ C$)$ Determining the maximum allowable gas flow rate.

$-$ D$)$ Indicating the necessary diameter for the column.

$32.$ The height of a transfer unit $($HTU$)$ in a packed column is important for:

$-$ A$)$ Estimating the column's pressure drop.

$-$ B$)$ Determining the column's operating costs.

$-$ C$)$ Calculating the total height required for the desired separation.

$-$ D$)$ Selecting the appropriate solvent for the process.

$33.$ Analytical methods for determining the number of stages in an absorption process are necessary when:

$-$ A$)$ The equilibrium curve is not known.

$-$ B$)$ The process involves a series of complex reactions.

$-$ C$)$ Accurate and detailed design specifications are required.

$-$ D$)$ The solvent and gas have similar densities.