The last step in the formation of the hybrid orbitals of a carbon atom is illustrated in the orbital diagram below. Which of the following statements most accurately sums up what happened prior to the step depicted in the diagram? 
(a) three electrons fill up the 2p atomic orbital
(b) the promotion of an electron into the 2p atomic orbital from the 2s orbital(c) the 2s orbital becomes three orbitals

• A. three electrons fill up the 2p atomic orbital
• B. the promotion of an electron into the 2p atomic orbital from the 2s orbital
• C. the 2s orbital becomes three orbitals