in the pliocene epoch, coniferous forests and covered much of the north.
tropical rain forests
grasslands
deserts
tundra

  Tundra.

Explanation:

  The Pliocene epoch is the second and youngest of the Neogene Period in the Cenozoic Era, the one that we still living today.

  In which respects the climate, it was dyer and cooler than the prior epoch and it affects the vegetation of the Pliocene by reducting the tropical species worldwide. In the north, there was a vast amount of coniferous forests and tundra, while the tropical forests were limited to a band near the equator line.

  I hope this answer helps you.

c. is the correct answer