There are 4 valence electrons in an atom of carbon. Carbon is in group 4A of the periodic table. There are 6 electrons in a carbon atom but only 4 of them are valence. carbon can never form more than 4 bonds and is unhappy with less than 4.
B because it takes in nutrients through endocytosis so the membrane opens up and envelopes the nutrients
C because oxygen was a byproduct of photosynthesis and proved to be EXTREMELY important in the atmosphere.
The white blood cell identifies the toxin produced by the pathogen and creates antibodies to fight the pathogen
