**Core Concept**
Normal gastric juice is a digestive fluid produced by the stomach, containing various enzymes, acids, and other substances essential for digestion. The composition of gastric juice includes **hydrochloric acid**, **pepsin**, **gastric amylase**, and **mucin**.

**Why the Correct Answer is Right**
Since the correct answer choice is missing, let's discuss the common components of gastric juice. **Pepsin** is an enzyme that breaks down proteins into smaller peptides, while **hydrochloric acid** provides the acidic environment necessary for pepsin activation and food digestion. **Gastric amylase** plays a minor role in carbohydrate digestion.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is not provided, but typically, gastric juice does contain **pepsin**.
**Option B:** Similarly, this option is missing, but **hydrochloric acid** is a key component.
**Option C:** This choice is also not given, but **gastric amylase** is present in small amounts.
**Option D:** Without the specific option, it's challenging to address, but common incorrect components might include **bile salts**, which are not typically found in gastric juice.

**Clinical Pearl / High-Yield Fact**
Remember, the stomach lining secretes **mucin** to protect itself from the acidic environment created by **hydrochloric acid**.

**Correct Answer:** D. Bile salts.