Which characteristic best distinguishes glycolysis and the krebs cycle from the electron transport chain?
a. the amount of atp produced
b. the location in which they occur
c. whether glucose is broken down
d. whether they occur in plants or animals

The correct answer is A. the amount of ATP produced.

The three reactions of the aerobic respiration in order are glycolysis, Kreb's cycle and the electron transport chain.

These processes are common to plants and animals and in the first step of respiration which is glycolysis the glucose breaks down.  Only glycolysis occurs in the cytoplasm of the cell while both Kreb's cycle and electron transport chain occurs in mitochondria. In the question the difference is asked between glycolysis and krebs cycle to the electron transport chain.  The initial two processes differ to the electron transport chain in terms of the number of ATP molecules generated. Both  glycolysis and the Kreb's cycle generate 2 ATP each respectively but the electron transport chain produces a net of 34 ATP molecules and therefore, electron transport chain differs from glycolysis and  Kreb's cycle in terms of the amount of ATP produced.