The stability of `+1` oxidation state increases in the sequence :

Options

A. `Ga lt In lt Al lt Tl`
B. `Al lt Ga lt In lt Tl`
C. `Tl lt In lt Ga lt Al`
D. `In lt Tl lt Ga lt Al`

Answer

B

Explanation

Due to inert pair effect, `Ga, In`, and `Tl` exhibit `+1` as well as `+3` oxidation states. The stability of `+1` increases on moving down the group. `B` shows only `+3` oxidation state while for `Al, +1` state is unstable. The `+1` oxidation state is the most stable for `Tl`.