Cycads and ginkgoes were important plants to the world's terrestrial ecosystems during the (select one):

a. paleozoic era
b. cenozoic era
c. mesozoic era
d. precambrian

Option (C)

Explanation:

Cycads and ginkgoes are two non-flowering, gymnosperms plants, and are comprised of both the male as well as female reproductive organs found in separate plants. These plants that are found today are very complex and have undergone an evolution. They were highly common during the Jurassic period and the herbivore dinosaurs were dependent on these types of plants.

Cycads and ginkgoes were most abundant during the Jurassic period of the Mesozoic era. The Jurassic period is also considered to be the 'age of cycads'.

Thus, the correct answer is option (C).