$18.$ True or False: Continuous contact extractors do not allow for the recycling of solvent within the system.

$19.$ True or False: The choice of solvent has a significant impact on the environmental footprint of the extraction process.

$20.$ True or False: Co$-$current and counter$-$current extraction methods can be applied interchangeably without affecting the outcome.

$21.$ True or False: Solvent loss is a critical factor in determining the sustainability of an extraction process.