Natural gas is primarily composed of methane and higher hydrocarbons. Methane is the main component and typically makes up the majority of natural gas, usually around 70-90% of its composition. Higher hydrocarbons, such as ethane, propane, and butane, are also present in smaller quantities.

Option 2, "butane and isobutene," is not correct because while these hydrocarbons can be found in natural gas in trace amounts, they are not the main constituents.

Option 3, "methane only," is also incorrect. While methane is the dominant component, natural gas contains other hydrocarbons as well.

Option 4, "methane, hydrogen, and carbon monoxide," is not accurate as hydrogen and carbon monoxide are not typically found in significant quantities in natural gas.

Therefore, option 1, "methane and higher hydrocarbons," is the correct answer as it accurately reflects the main components of natural gas.