A. H2O
B. NaCl
C. CO2
D. Mg
Answer
Correct Answer: D. Mg
Detail about MCQs
Among the options given, Mg (magnesium) is not a compound. It is an element, represented by its chemical symbol on the periodic table. H2O (water), NaCl (sodium chloride), and CO2 (carbon dioxide) are all compounds made up of multiple elements chemically bonded together.