In order to learn to be one's true self, it is necessary to obtain a wide and extensive knowledge of what has been said and done in the world, critically to inquire into it; carefully to consider it; clearly to analyze it; and earnestly to carry it out.
It matters not what you learn, but when you once learn a thing, you must never give it up until you have mastered it. It matters not what you inquire into, but when you once inquire into a thing, you must never give it up until you have thoroughly understood it. It matters not what you try to think of, but when you once try to think of a thing, you must never give it up until you have got what you want. It matters not what you try to carry out, but when you once try to carry out a thing, you must never give it up until you have done it thoroughly and well.
If another man succeeds by one effort, you will use a hundred efforts. If another man succeeds by ten efforts, you will use a thousand.
According to the author, first of all one must______.

A. analyze
B. inquire
C. obtain knowledge
D. act