
Complete Question
The complete question is shown on the first uploaded image
Answer:
a
The correct option is reagent B
b
The  skeletal structure of major organic product A is shown on the third uploaded image
Explanation:
The mechanism of the reaction for A and  B  are shown on the second the second reaction and looking at this we can see that the reagent that  predominately gives 1,2 addition is reagent B Â