— Volunteering is becoming _____ popular in China.

— Yeah, people are now aware that helping others is helping themselves. [ ]

A. naturally

B. successfully

C. splendidly

D. increasingly

孙中山在香港求学期间，与陈少白、杨鹤龄、陆皓东等人交往甚密。他们四人在一起谈论革命言论，怀有革命思想，研究革命问题。