Boys originally accounted for 1 of the total number of students in the whole group, while boys were1/3/(1-kloc-0//3) =1/2.

After adding four male students, it accounts for half of the total number of the group, that is,1/2/(1/2) =1.

That is to say, there are four female students 1- 1/2= 1/2.

There are four female students +0/2 = 8.

Originally: 8÷(2/3)= 12 people.

A: There are 12 students in the extracurricular activity group.