What causes the differences in physical characteristics like hair color among people?

A: different version of genes

B. Variations in DNA length

C. Different number of chromosomes

D. Variations in nucleus size

Hurry in a test

Which greenhouse gas is emitted when burn fossil fuels for energy? a. nitrogen b. oxygen c. carbon dioxide d. helium

The same agricultural practices are used in every country of the world. select the best answer from the choices provided t f

Fossils of ancestors of the modern horses show a small 4-toed almost dog-like browsing animal named eohippus over time the horses got larger lost toes and changed to a grazing diet what is the best explanation of why this change occurred