①基层政权开展民主管理、实行村民自治

②村“两委”在村民自治中发挥重要作用

③基层民主制度有利于维护村民的合法权益

④社会公示制度确保村民自治制度化、规范化

    There are forty-eight students in our class. There are twenty-three boys and twenty-five girls. Some students live near the school, and some others live very far from the school. About half of the students come to school by bike. They often get to school at a quarter to seven. About ten students often come to school by bus. They often go to school very early, too. Another ten students come to school on foot. Their homes are near the school, but they are often late for school, because they get up very late.

下图为人体血液循环模式图，请据图回答

（1）人体血液循环分为两种，图中能完整表示出的是____ 循环，该循环的起点是____ 
（2）在心脏①与②、③与④之间，有防止血液倒流的____ ，保证血液在心脏只能从心房→____ →动脉．
（3）结构8的名称是____ 。
（4）当血液流经 6 ____ 时，血液中的氧含量将会____ ，血液变为____ 。