To solve this problem, we need to match the microorganisms in List I with the products they are associated with in List II. Let's analyze each microorganism:$\newline \bullet$a. Aspergillus niger: This microorganism is known for producing citric acid.$\newline$ - This matches with iii.$\newline \bullet$b. Acetobacter aceti: This bacterium is used in the production of acetic acid.$\newline$ - This matches with i.$\newline \bullet$c. Clostridium butylicum: This bacterium is known for producing butyric acid.$\newline$ - This matches with iv.$\newline \bullet$d. Lactobacillus: This bacterium is involved in the production of lactic acid.$\newline$ - This matches with ii.$\newline$Now, let's match the items from List I with List II:$\newline a \rightarrow iii, b \rightarrow i, c \rightarrow iv, d \rightarrow ii \newline$This corresponds to Option 1, which is the correct option.