Final answer:
The fluid with high levels of Na⁺ and HCO₃⁻ and low levels of Cl⁻ and K⁺ is gastric juice, which is produced in the stomach and aids in the digestion of food.
Step-by-step explanation:
The fluid that shows a high composition of Na⁺ (sodium) and HCO₃⁻ (bicarbonate), and low levels of Cl⁻ (chloride) and K⁺ (potassium) is gastric juice. Gastric juice is produced by glands in the stomach and contains water, inorganic ions, hydrochloric acid, enzymes, and proteins. It plays an important role in the digestion of food.