Three ammeters P,Q and R with internal resistances r, 1.5r, 3r respectively. Q and R parallel and this combination is in series with P, the whole combination is in series with P, T the whole combination connected between X and Y. When the battery connected between X and Y, the ratio of the readings of P, Q and R is
A. `2:1:1`
B. `3:2:1`
C. `3:1:2`
D. `1:1:1`