Answer:
B
Step-by-step explanation:
Wendy and Ian didn't want to move, but they were outvoted by their parents. As a result, they stayed in their house rather than befriending the kids in their new neighborhood. They did this out of annoyance with their parents for being forced to move. This shows that Wendy and Ian responded to the conflict (having to move) by "staying inside and sulking." The development in the plot is seen when they go on to make friends that lived just around the corner; showing that if they had gone outside, rather than angrily sulking inside, they would've made friends weeks prior. Therefore, the answer is B.