<span>The most likely explanation for the lack of significant warming at the Earth's </span>surface<span> in the past decade or so is that natural climate cycles </span>caused<span> shift.</span>
At the very least, an oxoacid must 1) be an acid and 2) contain oxygen.
Ba(OH)2 (barium hydroxide) is a strong base. HCN, HF, and hydrochloric acid (HCl) don't contain oxygen.
Nitrous acid (HNO2) is an acid, and it contains oxygen. And the acidic hydrogen is bonded to an oxygen. Thus, nitrous acid qualifies as an oxoacid.
I don't know if H2PO4 is a typo; if not, then it would properly be written as H2PO4⁻ since it's the first deprotonation product of phosphoric acid, H3PO4. In any case, H2PO4⁻ is still acidic, albeit weakly, and its acidic hydrogens are bonded to the oxygen atoms. Thus, "H2PO4" would qualify as an oxoacid (for that matter, H3PO4 would also be an oxoacid).
Chloric acid (HClO3) is an acid, and it contains oxygen; its acidic hydrogen is bonded to an oxygen atom. Thus, chloric acid qualifies as an oxoacid.
Answer: option B and option C
Explanation: