Which statement about carbon dioxide and methane is correct?
- ACarbon dioxide: formed when vegetation decomposes ($\checkmark$); Methane: formed when vegetation decomposes ($\times$)
- BCarbon dioxide: greenhouse gas ($\checkmark$); Methane: greenhouse gas ($\checkmark$)
- CCarbon dioxide: present in unpolluted air ($\times$); Methane: present in unpolluted air ($\times$)
- DCarbon dioxide: produced during respiration ($\times$); Methane: produced during respiration ($\checkmark$)