What advancements helped Earth’s human population to grow so quickly?

Can someone me with this and tell me what’s fracking and what does it have to do with carbon, carbon dioxide, or fossil fuels?

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.

15 ! come and answer! a(n) is the general term for an infectious disease that has spread across a city, region, or country.