Which two factors could be controlled to make the result of the investigation more valid ​

How does the molecular clock work? a. it analyzes the brain functionality of two different species. b. it examines and compares the physical characteristics of two different species. c. it illustrates relationships between two different species. d. it compares the number of mutations that exist in the dna of two different species.

Witch type of microscope is used to view very small cell components like proteins and dna?

Explain why ecosystem diversity results in species diversity in a healthy biosphere