- **Nitrous oxide:** It's a potent greenhouse gas. It traps heat in the atmosphere, contributing significantly to global warming.

- **Water vapour:** This is the most abundant greenhouse gas. It amplifies the greenhouse effect, as more water vapour can absorb more heat.

- **Surface level ozone:** This is a minor greenhouse gas. It contributes to warming but also harms human health and vegetation at ground level.

- **Helium:** It's an inert gas and not a greenhouse gas. It does not trap heat and has little interaction with the earth's atmosphere.

- **✅ Helium** is the correct answer as it is not a greenhouse gas.

YOUR ANSWER IS RIGHT.