Concept:Cappling and staking are cultural practices that mainly support the growth of yam plants in the field.
Explanation:Cappling involves covering young yam shoots with soil, which helps in tuber formation and protects the growing plant.
Staking provides support for the climbing vines of yam, allowing them to grow upwards and receive enough sunlight and air.
Yams have weak, trailing vines, so they need stakes to climb and spread well.
Tomatoes are staked, but the question refers to the combined practices of cappling and staking, which are common in yam cultivation.
Sweet potatoes and groundnuts do not usually require staking because their vines or plants grow close to the ground.
Hence, cappling and staking are most important when cultivating yams.
Answer:C - yams