The correct answer is option 2, CF4. This is because CF4, also known as carbon tetrafluoride, exists as a gas under ordinary conditions and room temperature.

Let`s look at the other options to understand why they are not correct:

Option 1: Cl4 (tetrachloride) does not exist as a gas under ordinary conditions and room temperature. It exists as a liquid at room temperature.

Option 3: CCl4 (carbon tetrachloride) also does not exist as a gas under ordinary conditions and room temperature. It exists as a liquid at room temperature.

Option 4: CBr4 (carbon tetrabromide) does not exist as a gas under ordinary conditions and room temperature. It exists as a solid at room temperature.

It is important to note that the physical state of a chemical substance can vary depending on the temperature and pressure conditions. In this case, CF4 is the only substance among the options that is a gas under ordinary conditions and room temperature.