Which of the following would not be a good choice for reducing nitrobenzene to aniline?

If molality of a dilute solution is doubled, the value of the molal elevation constant $$\left(\mathrm{K}_{\mathrm{b}}\right)$$ will be

Hydrolysis of sucrose is called

Which one of the following has lowest $$\mathrm{pK}_{\mathrm{a}}$$ value?