$5.$ What is the principle of cross$-$current extraction?

$-$ A$.$ The same solvent is used in each stage, with fresh solvent for each new stage.

$-$ B$.$ The feed moves in the opposite direction to the solvent.

$-$ C$.$ The feed and solvent are mixed together in a single container.

$-$ D$.$ The solvent is recycled in each stage.

$6.$ What is the main advantage of co$-$current extraction?

$-$ A$.$ Higher purity of the final extract

$-$ B$.$ Lower solvent usage

$-$ C$.$ Easier phase separation

$-$ D$.$ Faster equilibrium attainment

$7.$ In counter$-$current extraction, what is the direction of solvent flow compared to the feed?

$-$ A$.$ The same direction

$-$ B$.$ The opposite direction

$-$ C$.$ Perpendicular

$-$ D$.$ No specific direction

$8.$ What is the main benefit of using a multistage extraction process over a single$-$stage process?

$-$ A$.$ It requires less solvent.

$-$ B$.$ It achieves higher purity of the extract.

$-$ C$.$ It is faster.

$-$ D$.$ It requires less energy.