Which event allowed greater diversity of life during the paleozoic era?

Option C, animals moved from the sea to the land is the right answer.  

The Paleozoic Era in the history of the earth was a time of major change on Earth. This was the period that ran about 542 to 251 million years ago. The period commenced with the split of a single super-continent and the development of another. Plants grew extensively. Moreover, the primary vertebral animals conquered the land.

The correct answer is option C

The events that aid for the greater diversity of organism is the movement of organisms or animals from the sea to the land.

The terrestrial organisms are not visible as they live in water.

But as soon as they moved towards land they were visible and reproduced and diversity were seen at Paleozoic era.

not always but somethings can be reproduced in a laboratory.