The correct answer is option 4, bile juice.

When food passes from the stomach to the small intestine, it is in a highly acidic state due to the presence of gastric acid in the stomach. This acidic semi-digested food, also known as chyme, needs to be neutralized before further digestion and absorption can take place in the intestine.

Bile juice, produced by the liver and stored in the gallbladder, plays a crucial role in this neutralization process. Bile contains a substance called bile salts, which help to break down fats into smaller droplets. At the same time, bile also acts as an alkaline solution that neutralizes the acidic chyme coming from the stomach. The alkaline properties of bile raise the pH of the chyme, making it less acidic and creating an optimal environment for enzymes in the small intestine to function properly.

Therefore, bile juice, along with its bile salts, plays a significant role in neutralizing the acidic chyme from the stomach, allowing for efficient digestion and absorption of nutrients in the small intestine.