1. There is no social problem it is more incumbent upon us to understand than this of the role of custom.
    没有任何一个社会问题比得上风俗的作用问题更要求我们对它理解。

2. It is incumbent on you to give a father´s advice before your son leaves home.
    在儿子离家之前给他一点忠告，是作父亲应尽的义务。