True or false: the hydrogen atom is most stable when it has a full octet of electrons.

The answer in this question is FALSE. Hydrogen atom has electronic configuration 1s^1. It needs only one more electron to make a closed sub-shell. Therefore, a stable hydrogen atom does not have an octet but a duplet. Therefore, the statement is false.

Let's see. It's definitely not the O horizon, because that layer is at the very top. A is already eliminated. Same thing with the A horizon, that is actually the top soil. C is out. It has to be either B or D. A D layer doesn't exist, so B is out. But the B horizon is considered a region of subsoil. The answer is D: B horizon.