a) The normal oxide of carbon, CO; a colorless, odorless gas formed during respiration and combustion and consumed by plants during photosynthesis.
b) Compared to carbon monoxide, CO is a non-toxic gas, similar to the inert gases. Carbon dioxide is used on welding and lasers; unlike noble gases, it only reacts on water and minerals to produce carbonates and carbonic acid (chiefly referred as carbonation).
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