Which among the following cations will not form coloured compounds? (Atomic number $$\mathrm{Cu}=29, \mathrm{Ti}=22, \mathrm{~V}=23, \mathrm{Mn}=25$$)

Which of the following aldehydes is less reactive towards nucleophilic addition reaction?

Which of the following is an aldohexose?

Cannizzaro reaction is an example of