The correct answer is option 1: Methane. Methane is the primary component of natural gas. Natural gas is a fossil fuel that is formed deep within the Earth`s crust over millions of years. It is primarily composed of methane, which is a hydrocarbon compound consisting of one carbon atom and four hydrogen atoms (CH4).

Option 2: Butane is not the primary component of natural gas. Butane is a hydrocarbon compound that is commonly found in liquefied petroleum gas (LPG) and is often used as a fuel for heating and cooking.

Option 3: Propane is also not the primary component of natural gas. Propane is another hydrocarbon compound that is commonly found in LPG and is used as a fuel for various applications, such as heating, cooking, and transportation.

Option 4: Ethane is not the primary component of natural gas. Ethane is another hydrocarbon compound that can be found in natural gas, but it is present in smaller quantities compared to methane.

In summary, while options 2, 3, and 4 are hydrocarbon compounds that can be found in natural gas, the primary component of natural gas is methane.