Option B and Option C do not match mid = (Low +High)/2
Option D is same as the defective one mention in the question mid = (low +High)/2
so Eliminate option B , C and D
now , lets solve
mid = ( High – Low ) / 2 + Low
mid = (High – Low + 2Low ) /2
mid = ( High + Low ) / 2 → which is equivalent to mid = ( Low + High ) / 2 given in the question
so after solving we got option ( A) is correct answer .