为了探究环境因素对蚯蚓生活的影响，某学校生物兴趣小组的同学进行了如下探究，请帮助他们完成探究过程：
--- Lots of trees and flowers ________ in Zhangzhou every year.
--- You're right. That makes our city more and more beautiful.
下列四幅图中，磁感线的方向、磁极名称标注正确的是( )
