Scientists analyze found in lake bottoms to learn what type of plants lived there thousands of years ago

fossils

Explanation:

Some animal bodies will be crushed in mud or soil and make perfect prints of the animals body. Although the organic body decay, the pressured soil sample will remain for thousands of years without a difference till someone like scientist discover it by careful excavations or get deteriorated by natural disasters.

In this case fossils have been found at the bottom of a lake, which scientist can study and get a understanding about the structural organisation of bodies of creatures lived there thousands of years ago by being in there labs.

i already answered it by 34/s