Consider the following claims made about hydrogen enriched CNG (H-CNG) as a fuel for public transport buses:

1. It eliminates carbon monoxide emissions entirely

2. It reduces carbon dioxide and hydrocarbon emissions compared to ordinary CNG

3. Hydrogen can be blended with CNG up to roughly one-fifth by volume

4. Blending hydrogen makes the fuel cheaper to produce than plain CNG

Which of the claims given above are correct?