$26.$ When designing a packed column, the number of transfer units $($NTU$)$ is influenced primarily by:

$-$ A$)$ The solvent's chemical properties.

$-$ B$)$ The mass transfer coefficient.

$-$ C$)$ The packing material size.

$-$ D$)$ The temperature of the operation.

$27.$ The minimum solvent flow rate is determined by:

$-$ A$)$ The desired separation efficiency.

$-$ B$)$ The maximum allowable pressure drop.

$-$ C$)$ The physical properties of the solvent.

$-$ D$)$ The cost of the solvent.

$28.$ In an absorption column, if the liquid phase controls the rate of absorption$,$ this will affect the design by:

$-$ A$)$ Increasing the required column diameter.

$-$ B$)$ Decreasing the height of the column.

$-$ C$)$ Increasing the height of the column.

$-$ D$)$ Decreasing the solvent flow rate.

$29.$ The absorption factor $($AF$)$ affects the process design by:

$-$ A$)$ Indicating the solvent's capacity to absorb a specific gas.

$-$ B$)$ Determining the physical dimensions of the column.

$-$ C$)$ Influencing the choice of packing material.

$-$ D$)$ Affecting the temperature at which the process operates.