Nowadays, there are lots of left-behind children（留守儿童）at school, especially in the ____（贫穷）areas in China. According to report, China has 61.03 ____（million）children who have been left behind by their families. ____（lack）proper care, many of these children suffer from anxiety（焦虑）and ____（事故）.

    Some of left-behind children have ____（not see）their parents for more than a year. Some of them live with their grandparents or relatives. They feel ____（孤独）and miss their parents a lot. Every child needs ____ （parents）love and care.

    Zhi Yan, a 10-year-old girl, lives in a mountain village in ____ （west）China. She has to prepare supper for her family ____（除了）study. “Thanks to schools, governments and society's help, we live ____（happy）.” The girl said.

如图，在△ABC中，AB=AC，⊙O是△ABC的内切圆，它与AB，BC，CA分别相切于点D、E、F．

（1）求证：BE=CE；

（2）若∠A=90°，AB=AC=2，求⊙O的半径．

如图所示，重为8N的石块浸没在水中称重时为5N，则石块受到的浮力大小为（　　）