What is the valency of carbon? When carbon possesses three bonds,it does not have a charge; when does such a thing happen and why?

An element $(A)$ occurs in the short period having electronic configuration $ns^2 np^1$. The formula of its oxide will be

The number of elements among $O, Cl, F, N, P, Sn, Ti, K, Sc$ which show more than one non-zero oxidation state is:

Choose the incorrect formula out of the four compounds for an element $X$ below.

The nucleus of an element contains $9$ protons. Its valency would be:

Consider the elements:
$Cs, Ne, I$ and $F$
$(a)$ Identify the element that exhibits only negative oxidation state.
$(b)$ Identify the element that exhibits only positive oxidation state.
$(c)$ Identify the element that exhibits both positive and negative oxidation states.
$(d)$ Identify the element which exhibits neither the negative nor does the positive oxidation state.