The correct answer is option 4: wheat, rice, maize. These three crops contribute the most to global food grain production. Wheat is one of the most widely cultivated cereal crops and is a staple food for many countries. Rice is another major staple crop, particularly in Asia where it is a primary source of nutrition for billions of people. Maize, also known as corn, is a versatile crop that is widely grown for food, animal feed, and industrial purposes. These three crops have high yields and are able to adapt to a variety of climates and growing conditions, making them important for global food security. Barley and sorghum are also significant crops, but they do not contribute as significantly to global food grain production as the three crops mentioned in option 4.