To identify which of the given compounds is a base, let’s analyze them:

1. **Compound 1: KHCO₃ (Potassium bicarbonate)** - This is a basic compound as it can accept protons.
2. **Compound 2: HCl (Hydrochloric acid)** - This is an acid.
3. **Compound 3: H₂SO₄ (Sulfuric acid)** - This is also an acid.
4. **Compound 4: NaCl (Sodium chloride)** - This is a neutral salt, not a base.

Based on this analysis, the answer is **B. Compound 1 (KHCO₃)**, as it is the only base among the options provided.