To solve this problem, we need to match the organisms with the products they produce. Let's analyze each organism:$\newline \bullet$a. Lactobacillus: This bacterium is known for its role in the fermentation of milk to produce curd.$\newline \bullet$b. Saccharomyces cerevisiae: This yeast is commonly used in baking and brewing, where it helps in the production of bread.$\newline \bullet$c. Aspergillus niger: This fungus is used industrially to produce citric acid.$\newline \bullet$d. Acetobacter aceti: This bacterium is involved in the production of acetic acid, commonly known as vinegar.$\newline$