The part of the chemical reaction that is the Brønsted-Lowry base is BrO.
Bronsted-Lowry definition of a base and acid is as follows:
According to this question, the following chemical reaction is given:
BrO + H2CO3 → HCO3 + BrOH
In the above reaction, BrO is the compound that accepts the hydrogen ion (H+) to become BrOH, hence, BrO is the Bronsted-Lowry base.
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