Which of the following statements about oxygen concentrations is MOST accurate?

A. Materials that do not burn at normal oxygen levels will not burn in oxygen-enriched atmospheres.
B. Materials that burn at normal oxygen levels will ignite more slowly in oxygen-enriched atmospheres.
C. When the oxygen concentration is higher than normal, materials exhibit very similar burning characteristics.
D. At high ambient temperatures, flaming combustion may continue at much lower oxygen concentrations.

D