巴拿马运河沟通的大洋是(        )

    Mrs. Green works very long hours every day. She usually gets up(起床 ) at 5:40. She brushes her teeth(刷牙) and goes to her workplace (工作地点). Then she runs with some kids. After that she takes a shower(淋浴). she eats her breakfast at 7:00. Her work starts(开始) at 8:10. she is good at(擅长 ) history and many boys and girls learn history from her. All the kids（孩子） like her very much. She often talks or plays games with the kids. She  usually goes to bed(睡觉) after 22:00. she is often very tired(劳累) but she likes her job and loves the kids. She doesn't work on weekends. Mrs. Green likes reading at home on weekends(周末). Sometimes some kids' parents come to her home to talk about their kids. When Monday comes, Mrs. Green gets busy again.

在中国古代“家国一体”的社会中，忠孝观念源远流长，其源头是（  ）