在斯宾塞、博比特等人看来，以个人的社会生活为着眼点，凡是能促进人各类活动的课程内容，即为有用的课程内容。这属于课程内容选择的哪种原则？（ ）

(单选题)18.（ ） (单选题)17.（ ） (单选题)16.（ ） (单选题)—I wonder how much you charge for your services.—The first t (单选题)“The house ______ go to the daughter, not the son, according (单选题)I’ll never forget the days ______ I learn hard in my senior (单选题)I think of life as a good book. The further you get into it, (单选题)While he was investigating ways to improve the telescope, Ne (单选题)At this university, a medal together with a prize of certain (单选题)By the time he realizes he ______ into a trap, it’ll be too