I'm sorry i keep asking questions but i don't know this stuff

Hurry which of these is true about index fossils? a) are very scarcely found b) used as guides in relative dating c) found in the youngest layer of the rock d) used as reference points in absolute dating

Diagram of the evolution of land plants?

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?