Final answer:
A dog that ingests several onions may develop hemolytic anemia due to the oxidative damage caused by a substance in onions.
Step-by-step explanation:
A dog that has ingested several onions may develop hemolytic anemia. Onions contain a substance called N-propyl disulfide that can cause oxidative damage to red blood cells (RBCs), leading to their destruction. This results in a decrease in the number of functioning RBCs and subsequent anemia.