Which of the following factors does not explain why carbon can form so many compounds?
a. carbon can bond in chains and rings.
b. the same atoms can be grouped in different ways, forming isomers.
c. carbon can form four single bonds.
d. carbon has six protons in its nucleus.

D the number of protons is certainly important in carbon having the structure required to make so many compounds, but it doesnt directly explain why

There is one s orbital, and there are three p orbitals, five d orbitals, and seven f orbitals. thus, the answer is b. do not confuse the number of orbitals in a subshell with the number of electrons the subshell can hold. each orbital can hold two electrons, so the capacity of an nf subshell is 14 electrons.

The correct answer is d