(a)(i) Name the toxic substance found in specimen G (FRESH CASSAVA TUBER). (ii) Suggest four ways of removing the toxic substance named in (a)(i). (b) State...

(a)(i) Toxic substance in specimen G (fresh cassava tuber)

The toxic substance is hydrocyanic acid (prussic acid / hydrogen cyanide), derived from a cyanogenic glycoside.

(a)(ii) Four ways of removing the toxic substance

• Grating the tubers and squeezing out the juice under pressure.
• Soaking (steeping) the tubers in water for some days to ferment.
• Boiling or cooking the tubers thoroughly.
• Sun-drying or frying the grated mash.

(b) Two uses each of specimens I and J

Specimen I (onion bulbs):

• Used for flavouring food and eaten as a vegetable.
• Used medicinally and as a source of vitamins A and C.

Specimen J (pepper fruits):

• Used as a spice or condiment to flavour food.
• Used medicinally and as an insect repellant in stored produce.

(c) Four pests of specimen I (onion)

• Thrips.
• Onion maggot (onion fly).
• Nematodes (eelworm).
• Rodents.

(d) Two groups of crops to which specimens I and J belong (based on use)

• Vegetable crops.
• Spice (condiment) crops.