$BX_3 + NH_3 \xrightarrow{R.T} BX_3 \cdot NH_3 + \text{Heat of adduct formation } (\Delta H)$. The numerical value of $\Delta H$ is found to be maximum for

Select true or false statements :
$(a)$ Promotion of electron is essential condition prior to hybridisation
$(b)$ In $VSEPR$ theory,two or three electron pairs of a multiple bond are treated as a single super pair
$(c)$ Bond length for $CO_2$ lies between double and triple bonds
$(d)$ $Ne_2$ does not exist

The different types of bonds present in $CuSO_4 \cdot 5 H_2 O$ are

Which of the following compounds is not hypovalent but completes its octet?

Which of the following compounds $CANNOT$ act as a Lewis base?

What is the formal charge on the $C$ atom in the structure $S \equiv C - \ddot{N} :$?