"No two boys stand next to each other" meaning there are a maximum of 3 boys only. Hence, there are a minimum of 4 girls in the circle. 
insert pic  Seven children are standing in a circle. No two boys are standing next to each other. No three girls are standing next to each other. Which of these is true for the number of girls standing in the circle? 

[A] only 3 is possible 
[B] 3 and 4 are possible 
[C] only 4 is possible 
[D] 4 and 5 are possible 
[E] only 5 is possible 