Final answer:
Carbon dioxide is the acid anhydride of carbonic acid, whose chemical formula is H₂CO₃. Compound A, CH2O₃ (though typically written as H₂CO₃), represents carbonic acid, making it the correct answer.
Step-by-step explanation:
The acid anhydride of a compound is an oxide that reacts with water to form that acid. Carbon dioxide, CO₂, reacts with water to form carbonic acid, H₂CO₃, hence it is the acid anhydride of carbonic acid. When looking at the compounds listed as options, it can be noted that compound A: CH₂O₃ is indeed carbonic acid (although the formula should be written as H₂CO₃ to match the commonly accepted formula). The other options do not represent carbonic acid; those include carbon monoxide (B: CO), formaldehyde (C: CH₂O), and hypothetically hypochlorous acid (D: CHO₂), which is not the correct formula.