An organism is discovered that thrives both in the presence and absence of oxygen in the air. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight. This organism:.a) must use a molecule other than oxygen to accept electrons from the electron transport chain b) is a normal eukaryotic organism. c) is photosynthetic. d) is an anaerobic organism. e) is a facultative anaerobe.

A facultative anaerobe.

Explanation:

Anaerobes are organisms which can produce energy via the process of fermentation in the absence of oxygen. The anaerobes can be classified as facultative anaerobes and obligate anaerobes.

Facultative anaerobes are those which can carry out respiration in presence of oxygen but can choose to follow the fermentation pathway if oxygen is absent. Fermentation also uses glucose.

Aerobic respiration produces 32 molecules of ATP from one  molecules of glucose while fermentation produces only 2 molecules of ATP . Thus when the organism switches to fermentation pathway it utilizes more and more glucose to reach its energy demands.

Considering all the above points we can conclude that observations indicate that the organism is a facultative anaerobe.

they deliver oxygen to the blood