单项选择题

Writers learn as apprentices do except that they have no master to work for except themselves and the market.
The fact is that writing is an empirical art, which can only be learned by doing it. This fact is no reflection on the art of writing. Because skill is acquired in a seemingly haphazard way it is none the worse, indeed sometimes the better, for it. As in every art you must have at least the foundation of a gift, without which it is useless to proceed; but if the foundation exists, then success—not merely economic— is largely a matter of persistence and of making the most of opportunities. Experience is a hard school. Wastage among aspiring writers is high and most survivors have to rely on another job. The pros and cons of that situation are debatable. Working out in the world is not solely a form of insurance; it can also be a vital source of material and incentive, particularly for the fiction writer. Many well-known authors labored away at other jobs for part or all of their lives, and either profited there from or made their names notwithstanding.
Economic security frees the mind from worry, but a routine job also consumes mental energy which might otherwise be harnessed to creative output. This applies as much to freelance journalism and other ancillary activities of authorship as to nonliterary employment. A regular stint of reviewing, reading manuscripts for publishers, broadcasting, lecturing, and the like, may oil the machinery of the mind, but it may also use up horsepower to the point of exhaustion. Moreover, continuity of creation is often vital—whether for the construction of a work of fiction or for historical research or, indeed, for any idea that has to be digested into literary form. Interruptions nowadays, however, are a professional hazard that all authors have to contend with, but they are not insuperable and not the worst threat to a living literature.
According to the author, how is the skill of writing acquired

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