Question 2
What is the valency of helium, neon and argon?
The right answer is the one marked above.
0. The noble gases do not combine, so their combining capacity is nothing at all.
8 is a tempting wrong answer, because neon and argon do have 8 electrons in their last level. But that full outer level is exactly why they do not combine — they have no need to lose, gain or share anything. A full shell means a valency of zero.