Hydrochloric acid (HCI) is secreted from?

A. Liver; small intestine: Carbohydrate and protein digestion do not begin in the liver or the small intestine. The liver is involved in metabolism but not in the initial digestion of carbohydrates or proteins.

B. Mouth; stomach: Carbohydrate digestion begins in the mouth with salivary amylase, while protein digestion begins in the stomach with pepsin.

C. Small intestine; stomach: Carbohydrate digestion begins in the mouth and not the small intestine. Protein digestion starts in the stomach, not the small intestine.

D. Mouth; small intestine: Carbohydrate digestion begins in the mouth, but protein digestion begins in the stomach, not the small intestine.

A. Aerobic respiration; anaerobic fermentation: Aerobic respiration primarily occurs in the mitochondrion, and anaerobic fermentation occurs in the cytoplasm. Therefore, this is incorrect.

B. Glycolysis; the citric acid (Krebs) cycle: Glycolysis occurs in the cytoplasm, breaking down glucose into pyruvate. The citric acid (Krebs) cycle takes place in the mitochondrion, where it further processes pyruvate for energy production.

C. The citric acid (Krebs) cycle; mitochondrial electron-transport: Both the citric acid cycle and the mitochondrial electron transport chain occur in the mitochondrion.

D. Anaerobic fermentation; glycolysis: Glycolysis occurs in the cytoplasm and is the first step in both aerobic and anaerobic pathways, but anaerobic fermentation also occurs in the cytoplasm, so this option is not accurate in distinguishing between processes happening in different locations.