Carbon monoxide is the most common type of poisoning by gases
The significance of the spore formation during the reproductive cycle of the bacterium is that, it provide a defensive strategy against hostile and unfavorable conditions. The spore formation allows the bacterium to reproduce and spread even when the conditions are not favorable. The spore formation also make it possible for the bacterium to remain dormant over a long period of time during unfavorable conditions, waiting for the right conditions to become active again.
Carbon (C) is an element
Carbon Dioxide (CO2) is a compound
Hydrogen (H) is an element
Sodium Chloride (NaCl) is a compound
A good way to tell whether something is a compound or an element, is that in a compound there is a mixture of different elements. Like in Carbon Dioxide, the symbol is CO2. This shows the carbon (C) and oxygen (O) together. I hope i worded that well enough and this helps :)