What is is the average mass of a proton or a neutron? a) 1 amu b) 2 amu c) 3amu d) 4 amu

The answer is a) 1 amu

the positions which points up in upward carbon and down in downward carbon are axial

and vice versa holds true for equatorial positions

so the correct answer with labelled diagram will be

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).