What do alcohol fermentation, acetyl coa formation, and the krebs cycle have in common?

The correct answer is all reactions produce CO₂ as by-product.

Explanation:

The alcohol fermentation or ethanol fermentation is a biological process which converts simple sugars like glucose, fructose into ethanol and carbon dioxide as by-product performed by yeasts, moulds, or bacteria. One glucose molecule produces two molecules of  CO₂.

Link reaction is the reaction which links the process of glycolysis to citric acid or Krebs cycle by generating two molecules of acetyl-CoA from pyruvate producing CO₂ as a by-product through the process of decarboxylation.

Kreb cycle or citric acid cycle is the cycle which takes place after link reaction producing hydrogen and electron carriers needed for electron transport chain by converting acetyl CoA and forming CO₂ as a by-product. One glucose molecule produces 6 molecules of CO₂.

Thus, all reactions produce CO₂ as a by-product is the correct answer.

d. organisms have cells with different shapes and functions.