The correct option is A 1
In Ga, In and Tl, both +1 and +3 oxidations states are observed but +1 oxidations state of Tl is relative more stable.
The stability of +1 oxidation state among Al, Ga, In and Tl increases in the sequence Al<Ga<In<Tl.
This is due to inert pair effect due to which, on moving down the group, the stability of +3 oxidation state decreases while the stability of +1 oxidation state increases.
Hence correct option is a.