题目

One sunny afternoon, a seven-year-old girl went for a walk. She crossed a large area of grassland into the woods __16__ she realized that she was lost.     Sitting on a rock and __17__ what to do, she began crying. After a while，she__18__ to walk along a wide path lined with tall trees and thick bushes. __19__ it was getting dark, she saw a small, dark wooden house. She opened the door and __20__ stepped in. Suddenly, she heard a strange noise, and she ran out of the door and back to the __21__. Cold and tired, she fell asleep near a __22__.     The girl's parents were out an小芳同学在笔记中写到：“粉碎了帝国主义分裂中国的阴谋，标志着祖国大陆基本统一，实现了各民族的大团结。”据此判断，她学习的内容应该是（ ）A.抗美援朝 B.西藏解放C.香港回归 D.澳门回归