Protochlorophyll differs from chlorophyll in lacking
(a) 4 hydrogen atoms in two pyrrole rings
(b) 2 hydrogen atoms in one of its pyrrole rings
(c) 2 hydrogen atoms in two pyrrole rings
(d) 1 hydrogen atom in one pyrrole ring

Options

A. 4 hydrogen atoms in two pyrrole rings
B. 2 hydrogen atoms in one of its pyrrole rings
C. 2 hydrogen atoms in two pyrrole rings
D. 1 hydrogen atom in one pyrrole ring.

Answer

To determine how protochlorophyll differs from chlorophyll, we need to analyze the structure of both pigments and identify the specific differences in their composition.

### Step-by-Step Solution:

1. **Understanding the Structures**:
- Chlorophyll is a green pigment found in plants that plays a crucial role in photosynthesis. It has a complex structure known as a porphyrin ring, which consists of four pyrrole rings.
- Protochlorophyll is a precursor to chlorophyll and is formed from the oxidation of chlorophyll a.

2. **Identifying the Differences**:
- The question asks how protochlorophyll differs from chlorophyll in terms of hydrogen atoms in the pyrrole rings.
- Protochlorophyll specifically lacks two hydrogen atoms compared to chlorophyll.

3. **Locating the Missing Hydrogen Atoms**:
- The two hydrogen atoms that are missing in protochlorophyll are located at the 7th and 8th positions of the porphyrin ring structure.
- These positions are part of the pyrrole rings that make up the porphyrin structure.

4. **Evaluating the Options**:
- (a) 4 hydrogen atoms in two pyrrole rings: This is incorrect because protochlorophyll only lacks 2 hydrogen atoms.
- (b) 2 hydrogen atoms in one of its pyrrole rings: This is incorrect because the missing hydrogen atoms are not in just one pyrrole ring; they are in two different rings.
- (c) 2 hydrogen atoms in two pyrrole rings: This is correct as it accurately describes the missing hydrogen atoms in the two different pyrrole rings.
- (d) 1 hydrogen atom in one pyrrole ring: This is incorrect because protochlorophyll lacks 2 hydrogen atoms, not just 1.

5. **Conclusion**:
- The correct answer is (c) 2 hydrogen atoms in two pyrrole rings.

### Final Answer:
**(c) 2 hydrogen atoms in two pyrrole rings**