Explanation:

- Option 1: Gross output at MP

- Refers to the total value of goods and services produced before subtracting depreciation and indirect taxes but includes subsidies.

- Commonly used to describe overall production.

- Option 2: Net output at MP

- Represents the value of goods and services after deducting depreciation but before adjusting for taxes and subsidies.

- Focuses on the 'net' production value.

- Option 3: Gross output at FC

- Total production value at factor cost excluding indirect taxes and subsidies.

- Focuses on the cost incurred by producers.

- Option 4: None

- When none of the above apply or if it's specified differently in a text.

Option 1: Gross output at MP is correct.