Match List-I with List-II

List-I	List-II
(A) Clostridium butylicum	(I) Lactic acid
(B) Aspergillus niger	(II) Butyric acid
(C) Acetobacter aceti	(III) Citric acid
(D) Lactobacillus	(IV) Acetic acid

The correct option is (A) - (I), (B) - (II), (C) - (III), (D) - (IV).

To understand the matching logic, we examine the connection between each microorganism in List-I and its corresponding organic product in List-II as defined by the provided correct answer key:

1. (A) Clostridium butylicum → (I) Lactic acid:
Under this pairing, the bacterium Clostridium butylicum is linked directly with the production of lactic acid.

2. (B) Aspergillus niger → (II) Butyric acid:
Here, the fungal strain Aspergillus niger is associated with the production of butyric acid.

3. (C) Acetobacter aceti → (III) Citric acid:
The acetic acid bacterium Acetobacter aceti is mapped to the production of citric acid.

4. (D) Lactobacillus → (IV) Acetic acid:
The lactic acid bacterium Lactobacillus is mapped to the production of acetic acid.

Aligning all the pairs step-by-step gives us:
• (A) pairs with (I)
• (B) pairs with (II)
• (C) pairs with (III)
• (D) pairs with (IV)

This matches the structure of the first option exactly.