Among the given options, the pair that is not correctly matched is option 4. The statement in option 4 states that when the total product increases, the marginal product begins to decline. This is incorrect.
In economics, the concept of total product and marginal product is used to understand the relationship between inputs and outputs. Total product refers to the total quantity of output produced from a given amount of inputs, while marginal product refers to the additional quantity of output produced when one additional unit of input is added.
Options 1 and 2 are correctly matched. When the total product increases at an increasing rate, the marginal product also increases. On the other hand, when the total product increases at a diminishing rate, the marginal product declines.
Option 3 is also correctly matched. When the total product reaches its maximum point, the marginal product becomes zero. This means that adding more units of input does not result in any additional output.
In summary, among the given options, option 4 is not correctly matched. The correct pair is option 1, where the total product and marginal product increase at the same time.