Crop plant Petal colour Scent Pollen type Stigma Plant A (Cowpea) Purple / white Faint sweet Sticky, large grains Small, sticky Plant B (Tomato) Yellow Mild...

(a) The crop most likely to be wind-pollinated is Plant C (maize). [1]

Reason: maize has green flowers with no petals, produces no scent, has light smooth abundant pollen grains, and a long feathery stigma (silk). [1] All of these are classic adaptations for wind pollination: no need to attract insects, light pollen carried by air currents, and a large feathery stigma to catch airborne pollen.

(b) When pollen from Plant B (tomato) lands on the stigma of a different flower on the same plant, this is self-pollination. [1] Self-pollination is the transfer of pollen from an anther to a stigma of the same plant, whether within the same flower or between different flowers on the same individual.

(c) How a farmer carries out controlled cross-pollination to produce hybrid maize seed (4 marks):

1. Select the female parent plant and remove the tassels (male flowers) before they shed pollen. This process is called detasseling and prevents self-pollination. [1]
2. Cover the silk (female flower) with a paper or cellophane bag to prevent unwanted pollen from other plants reaching it. [1]
3. Collect fresh pollen from the tassels of the selected male parent plant. [1]
4. Carefully dust the collected pollen onto the exposed silk of the female parent, then re-cover with the bag to exclude any further uncontrolled pollination. [1]

This ensures the resulting seed carries genetic material from both chosen parents, producing F1 hybrid seed with predictable traits.

(d) Two advantages of using hybrid seed:

1. Higher yields due to hybrid vigour (heterosis): the F1 generation outperforms both parents in growth rate and productivity. [1]
2. More uniform crop: hybrid plants mature at the same time and are similar in height and quality, making harvesting and marketing easier. [1]

Other acceptable answers: improved disease resistance; better quality produce.