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.

小明为了证明蚯蚓喜欢阴暗的环境，他选择了两条蚯蚓，一条放在光下，另一条放在阴暗处。他的行为属于（   ）

学习了电学知识之后，小亮研究家中具有保温功能的电饭锅，画出电饭锅的电路原理图如图所示，电饭锅的铭牌上部分内容如下表．

（1）R₁、R₂中哪个是加热电阻？要使电饭锅加热，开关S闭合还是断开？
（2）电饭锅正常加热时，电路的电流是多大？
（3）电路中电阻R₁、R₂的阻值各是多大？保温时，R₁、R₂产生的电热之比是多少？

设双曲线  $\frac{y^2}{a^2}-\frac{x^2}{3}=1$的两个焦点分别为F₁、F₂离心率e=2.