Which of the Following Is(are) TRUE of Photoautotrophs

Multiple Choice

Which of the following is(are) TRUE of photoautotrophs?

A) They are responsible for the first concentration of free oxygen in the atmosphere.
B) They are responsible for an early extinction of most anaerobic organisms.
C) They are carbon-rich food baskets for heterotrophs.
D) They are responsible for the presence of the ozone layer of the atmosphere
E) All of these are true.