Concept:
Different microorganisms play important roles in:
• Food spoilage
• Industrial fermentation
• Food toxin production
• Food preparation
Step 1: Matching Aspergillus flavus.
Aspergillus flavus produces:
\[
\text{Aflatoxins}
\]
which contaminate food grains and nuts.
Thus:
\[
A \rightarrow IV
\]
Step 2: Matching Acetobacter aceti.
Acetobacter aceti converts ethanol into acetic acid and is used in:
\[
\text{Vinegar formation}
\]
Thus:
\[
B \rightarrow I
\]
Step 3: Matching Pseudomonas sp.
Pseudomonas species are common psychrotrophic bacteria involved in:
\[
\text{Spoilage of refrigerated meat}
\]
Thus:
\[
C \rightarrow II
\]
Step 4: Matching Rhizopus oligosporus.
Rhizopus oligosporus is used in fermentation of soybean products such as:
\[
\text{Tempeh}
\]
Thus:
\[
D \rightarrow III
\]
Step 5: Determining the correct combination.
Therefore:
\[
\boxed{
A\text{-IV},\
B\text{-I},\
C\text{-II},\
D\text{-III}
}
\]
Hence, the correct answer is:
\[
\boxed{(A)\ A\text{-IV},\ B\text{-I},\ C\text{-II},\ D\text{-III}}
\]