The correct answer is: d) River deltas.
Cole crops are a group of vegetables that includes cabbage, cauliflower, broccoli, Brussels sprouts, and kale. They are all members of the Brassica family, which also includes mustard, turnips, and rutabagas. Cole crops are cool-season crops, which means they grow best in cool, moist climates. They are not tolerant of hot, humid weather, and they will bolt (go to seed) if the temperature gets too high.
River deltas are ideal growing areas for cole crops because they provide the cool, moist climate that these crops need. River deltas are also rich in nutrients, which helps the crops to grow well. In addition, river deltas are often flat, which makes it easy to cultivate the land.
The other options are not as suitable for growing cole crops. Hot and humid coastal areas are too warm and humid for cole crops, and they are also more likely to be affected by pests and diseases. Cool hilly areas are too cool for cole crops, and they may not get enough sunlight. Dry interior plains are too dry for cole crops, and they may not get enough water.