The combining power (valency) of an element is the number of electrons which one atom of it readily gains or loses to attain the stable duplet or octet configuration of the noble gases. It is related to the oxidation number except that it does not have sign. Hence, for \(HCO _{3}^{-}, O , Na\) and \(Cl\), the combining powers are:
$$
HCO _{3}^{-} \rightarrow 1
$$
(it can still lose one electron)
\(O \rightarrow 2\)
(it gains two electrons to attain the octet configuration)
\(Na \rightarrow 1\)
(it readily loses an electron to attain the octet stability)
\(Cl \rightarrow 1\)
(it gains an electron readily to attain the stable octet configuration)
Therefore, the correct option is \(B (1,2,1,1)\)