The question asks for the increasing order of $pK_b$ for three compounds $(A)$, $(B)$ and $(C)$.

However, the actual structures of compounds $A$, $B$, and $C$ are not visible/provided in the prompt. Without the structures, the basic strength cannot be compared, because $pK_b$ depends on factors such as:

1. Inductive effect
2. Resonance effect
3. Hybridisation of the atom bearing the lone pair
4. Steric hindrance
5. Solvation effects

Since the compounds themselves are missing, a definite chemical comparison cannot be derived from first principles.

What can still be concluded

For bases:

• stronger base $\Rightarrow$ smaller $K_b^{-1}$ effect? More precisely,
• stronger base $\Rightarrow$ larger $K_b$
• hence stronger base $\Rightarrow$ smaller $pK_b$

So “increasing order of $pK_b$” means:

in terms of $pK_b$ values.

The stored correct answer is Option C:

Thus, according to the stored key, the basic strength order would be:

Limitation

Because the structures are absent, I cannot independently verify whether this order is chemically correct.

Therefore, I can only report that the stored answer is Option C, but this cannot be rigorously solved from the information shown.