The correct answer is D) arthropods.
During the Silurian period, the first animals to adapt to life on land were arthropods.
The Silurian period happened approximately 445 million years ago ant the end of the Ordovician period when the surface of the Earth was colling off. The glaciers melted and this accelerated the elevation of the seas. New forms of life started to appear in the sea. Others -for whatever reasons- decided to go to the land. That is when the arthropods started to be part of the landscape.
