The correct option is A H2(g)+Br2(g)→2HBr(g)
Since, for any reaction the relation between ΔH and ΔU is given by,
ΔH=ΔU+(Δng)RT where, Δng=change in gaseous moles
Hence, the reaction in which the value of Δng=0 will be the one with ΔH=ΔU
Since in option A, Δng=2−1−1=0
option B, Δng=2+1−2=1
option C, Δng=1+1−1=1
option D, Δng=2−2−1=−1
Hence, answer is A.