Concept:The diagram illustrates mixed cropping, where two different crops are cultivated together on the same farmland.Explanation:In this farm operation, a staking or tuber crop is planted alongside a spreading, low-growing crop.Yam serves as the main tuber crop and requires support to grow.Cowpea spreads along the ground, reduces soil erosion, and adds nitrogen to the soil.This combination is a common and suitable practice among farmers in the region.Answer:A. yam and cowpea