阅读下面短文，从短文后各题所给四个选项（A、B、C和D）中，选出可以填入空白处的最佳选项。

    10-year-old Penny goes back to her school to find a place for her dog Socks. The big door is 1. Penny walks around the school: there were doors at the 2. They are all locked. Then she sees a window. It is open. She 3 inside. She walks along the hallway between the classrooms. She can't put Socks inside a classroom.

    Under the classrooms, Penny finds a store room. It is locked, too, and she doesn't have the 4. Penny puts Socks on the ground and he runs along the hallway. Penny runs after him. “Come here,” she says. Socks is not 5. He runs into the girls' changing room.