the slow movement of tectonic plates the varying temperatures of each season an increase in volcanic activity under the oceans an increase in the number of photosynthetic organisms
I gave my students this multiple choice question: Some types of bacteria can only live where oxygen is not present. These bacteria were well adapted to life on Earth over 2 billion years ago. Which of the following changes caused many of these bacteria to become extinct?

Only one answer is correct among these 4 choices:
- the slow movement of tectonic plates
- the varying temperatures of each season
- an increase in volcanic activity under the oceans
- an increase in the number of photosynthetic organisms

Could you tell me which one is correct?

an increase in the number of photosynthetic organisms