.. Formulating Hypotheses Propose a hypothe- sis to explain why angiosperms have become the
dominant type of plant on Earth.

Brodribb and Feild argue that more photosynthesis meant more carbon for growth. And that would have given the angiosperms the energy to push competitors like conifers out of the canopy around 150 million years ago, making angiosperms the most productive group of land plants in the world.

c is the correct answer!