As we pressed our faces to the windows to look at the yard , I could n't help but wonder why we would need a key to unlock a door from the inside .

Choose your answer from: a. It was a security feature to prevent them from sneaking out . b. It was a way to remind the owner to always have their house keys . c. It was a mistake made by the person who installed the door . d. It was a way to play a prank on guests trying to leave the house .
Answer the following question: What may be the reason a key was needed to unlock the door .
a.