A worker who processes garri is engaged in

Aids to trade are grouped by the kind of change they make to a raw material or product. Extracting removes a resource directly from nature, such as mining or fishing, while constructing puts up fixed structures such as roads, bridges, or buildings.

Processing garri involves taking cassava, a raw agricultural product, and transforming it through peeling, grating, fermenting, frying, and other stages into a completely new, different product. Changing raw materials into a new form or finished product in this way is manufacturing.

Exchange refers to activities such as buying and selling that transfer ownership of goods without changing what the goods physically are, which does not describe what happens when cassava is turned into garri. Extracting would apply if the worker were harvesting the raw cassava itself from the ground, and constructing has no connection to food processing at all.

Whenever a question describes a raw material being physically transformed into a new usable product, classify that activity as manufacturing.