Correct Answer: carbon dioxide

Solution : The correct option is carbon dioxide.

Ocean acidification is the global drop in seawater pH caused by the oceans absorbing significant amounts of carbon dioxide (CO ₂ ). The primary cause of ocean acidification is the massive amounts of CO ₂ that automobiles, industries, and agricultural activities release into the sky. The oceans have absorbed between one-third and half of the CO ₂ that humans have produced into the atmosphere since the start of the Industrial Revolution, which was around 1750.