Assess students' understanding of ocean acidification: anthropogenic CO2 uptake and its drivers; key carbonate-system reactions (CO2 dissolution, carbonic acid, bicarbonate, carbonate, H+ increase); consequences for pH, carbonate ion concentration, and calcite/aragonite saturation; and ecological effects on marine calcifiers (reduced calcification, weaker shells, impaired larval stages, food-web impacts). Include interpretation of simple carbonate equations, saturation-state graphs, and short data-analysis questions.