The type of fermentation observed in yeasts is

The correct option is alcoholic fermentation.

Fermentation is an anaerobic biological pathway that breaks down sugars like glucose to produce energy in the absence of oxygen. In yeasts (such as Saccharomyces cerevisiae), the specific pathway utilized is alcoholic fermentation, also known as ethanol fermentation.

During this process, glucose is converted via glycolysis into pyruvate. Yeast then processes the pyruvate in two steps:
1. Decarboxylation of pyruvate to form acetaldehyde and carbon dioxide (CO₂).
2. Reduction of acetaldehyde to ethanol (ethyl alcohol) by the enzyme alcohol dehydrogenase, using NADH.

The overall simplified chemical equation for alcoholic fermentation is:
$$C_6{H}_{12}{O}_6\to 2C_2{H}_{5}OH+2C{O}_2$$
This biological process is fundamental in breadmaking (where the escaping CO₂ gas causes the dough to rise) and in the brewing and winemaking industries to produce ethanol.