Which one of the following is the correctly matched pair of a product and the micro-organism responsible for it?

Correct answer: (a) Ethyl alcohol — Yeast

Explanation

Only ethyl alcohol – yeast is correctly matched. Yeast (*Saccharomyces cerevisiae*) ferments sugar into ethyl alcohol and carbon dioxide, which is the basis of brewing and baking.

The correct micro-organisms for the others are:

• cheese and curd: lactic acid bacteria such as *Lactobacillus* (*Nitrobacter* is a nitrifying soil bacterium);
• acetic acid (vinegar): *Acetobacter aceti*;
• *Azotobacter* is a free-living nitrogen-fixing soil bacterium used as a biofertiliser.