Which of the following fuels has a flashpoint above 45°?

The correct answer identifies gasoline as having a flashpoint above 45°C. Flashpoint is the lowest temperature at which a liquid can vaporize to form an ignitable mixture in air. Gasoline has a flashpoint between approximately -40°C and 0°C, which is well below 45°C, making this information inconsistent with the question, as it seeks a fuel with a flashpoint above that temperature.

Natural gas, hydrogen, and acetylene have significantly lower flashpoints as well; natural gas, which is primarily methane, is not a liquid and therefore does not have a flashpoint in the traditional sense, but it does ignite easily at any temperature. Hydrogen also ignites very easily, often at room temperature, and acetylene has a flashpoint of around 17.8°C, again under the threshold specified.

In summary, none of the choices provided actually meet the criteria of having a flashpoint above 45°C. For example, the flashpoints for these fuels are all either significantly lower than 45°C or do not apply in the same way for gases. Hence, none of the options represent fuels with a flashpoint above 45°C.