[单项选择]By far the most common difficulty in study is simple failure to get down to regular concentrated work. This difficulty is much greater for those who do not work to a plan and have no regular routine of study. Many students muddle along, doing a hit of this subject or that, as the mood takes them, or letting their set work pile up until the last possible moment.
Few students work to a set time-table. They say that if they did construct a timetable for themselves they would not keep to it, or would have to alter it constantly, since they can never predict from one day to the next what their activities will be. No doubt some temperaments take much more kindly to a regular routine than others. There are many who shy away from the self-regimentatign of a weekly time-table, and dislike being tied clown to a definite programme of work. Many able students claim that they work in cycles. When they become interested in a topic they work on it intensively for three or four days at a time.
A. the failure to keep to a routine of methodical and intensive work
B. changing from one subject to another
C. unwillingness to follow a systematic plan
D. applying oneself to a subject only when one feels inclined