Answer:
The appropriate reagent is: H3PO2.
Explanation:
H3PO2 is in charge of eliminating the amino group by diazotization, remember that the amino group had previously achieved bromination at positions m; that is to say that it achieved in the beginning that the three bromine atoms of 1,2,4 tribromobenzene were introduced in the meta positions among themselves, which finally corresponds as part of the last reaction to the 1,3,5-tribromobenzene position.
