Scientists are studying the evolution of the sloth. They have fossils from 30, 20, 15 and 10 million years ago. Which fossil is most similar the the modern-day sloth? *

30 million years ago

Explanation:

Sloths are slow moving animals and are also cute animals. These animals are  mostly found in Central America and South America.

From many many million years sloths have lived on this planet. Sloth have evolved from elephant size to moose size in the past few million years. But scientist have known very little about their nature and about their species.

There are about many fossils from 30 million years to 10 million years but recently scientist have discovered that the fossils of sloth from the 30 million years ago are similar to the modern day sloth.  

substitution is the answer in this case