Step 1: Understanding the term 'prairies'.
Prairies are extensive flat or gently rolling grasslands found mainly in the central part of North America, particularly in the United States and Canada.
Step 2: Characteristics of prairies.
These regions are dominated by grasses and have very few trees due to moderate rainfall. They are often called the “granaries of the world” because of the large-scale grain cultivation.
Step 3: Conclusion.
Thus, prairies are best described as grasslands. The correct answer is (A).