Carbon sometimes forms tetrahedral shaped molecular structures. which property of carbon best explains this?
a. carbon's six protons.
b. carbon's four valence electrons.
c. carbon's three distinct allotropes.
d. carbon's average atomic mass of approximately twelve amu.

A tetrahedral shaped molecule involves a central atom (in this case carbon) covelantly bonded with four other atoms with out any lone pars.  Since carbon has four unpaired valence electrons, it would make sense that it can form 4 bonds with other atoms.  All of the other choices don't really directly affect the type of bonds that can be formed.  A common example of a tetrahedral structure is CH₄.