Which of the following root crop is the most useful for intercrop and companion planting?

Answer: Option C

Radish is the root crop that is the most useful for intercrop and companion planting.
Intercropping is the practice of growing two or more crops in proximity. The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources that would otherwise not be utilized by a single crop.
Companion planting is where two or more species are sown together to harvest the grain of a single species.
Radish as companion plants include lettuces, tomatoes, carrots, onions, peppers, peas, cucumbers and spinach as well as herbs like dill, mint and oregano. The radishes will mature before most other crops and help break up the soil as they grow.