Which of the following compound CANNOT act as a Lewis base?

The solubility of Ca(OH)₂ in water is :

[Given : The solubility product of Ca(OH)₂ in water = 5.5 $$\times$$ 10^$$-$$6]

The solubility of AgCN in a buffer solution of pH = 3 is x. The value of x is : [Assume : No cyano complex is formed; K_sp(AgCN) = 2.2 $$\times$$ 10^$$-$$16 and K_a(HCN) = 6.2 $$\times$$ 10^$$-$$10]

Arrange the following solutions in the decreasing order of pOH :

(A) 0.01 M HCl
(B) 0.01 M NaOH
(C) 0.01 M CH₃COONa
(D) 0.01 M NaCl