The correct answer is: a) Select foothill areas
Tea and coffee are plantation crops that are grown in tropical and subtropical climates. They require a warm, humid climate with well-drained soil. Foothill areas are ideal for growing these crops because they provide the necessary climate and soil conditions.
Option b, high altitude regions, is incorrect because tea and coffee plants do not grow well in high altitudes. They prefer a lower altitude with a warmer climate.
Option c, river valleys, is incorrect because river valleys are often prone to flooding, which can damage tea and coffee plants.
Option d, desert areas, is incorrect because desert areas are too dry for growing tea and coffee.
In conclusion, the correct answer is: a) Select foothill areas.