Oxyntic cells/peptic cells of gastric glands secrete HCI.

Explanation

### Step-by-Step Solution:

1. **Identify the Cells in Gastric Glands**: The gastric glands in the stomach contain three main types of cells: mucous neck cells, peptic (or chief) cells, and parietal (or oxyntic) cells.

2. **Function of Mucous Neck Cells**: Mucous neck cells secrete mucus, which serves to protect the stomach lining from the harsh acidic environment created by gastric secretions.

3. **Function of Peptic (Chief) Cells**: Peptic cells produce pepsinogen, an inactive precursor of the enzyme pepsin, which is involved in protein digestion.

...