The behavior of the consumer who are the one to decide with regards to select, purchase and then consumption of goods as well as services for the satisfaction of their needs and want is known as consumer behavior. The cardinal approach is focused on consumer view on utility.
Suppose you have a budget of Rs. 10 per week. You can spend your money on potatoes at Rs. 2 per kg or tomatoes at Rs. 1 per kg or on some combination of the two. The consumption opportunity line or budget line shows all possible combinations.