Imagine That Your Uncle Is a Scientist Who Has Found

Imagine that your uncle is a scientist who has found himself in possession of a time machine. The two of you travel back to the Paleozoic Era, and are perusing the oceans for microscopic life. What will you find?

A) only organisms reminiscent of red algae
B) some photosynthetic organisms, but these would be limited only to cyanobacteria and algae
C) an array of photosynthetic organisms, including cyanobacteria, dinoflagellates, and diatoms
D) radiolarians and other organisms with either silica or calcium-carbonate shells
E) some photosynthetic organisms (cyanobacteria and green algae) , and radiolarians and other heterotrophic protists