Given the task definition and input, reply with output. In this task, you're given an article, a question which often contains a blank and four options (associated with "A", "B", "C", "D"). Your task is to find the correct answer (from the given options) for the question from the given article and return one of the options from "A", "B", "C", and "D". Do not generate anything else apart from one of the following characters: "A", "B", "C", "D". There is only one correct answer for each question.

Article: One day a teacher was giving her young students a lesson on how the government works . She was trying to explain the principle of income tax . "You see ," she began , speaking slowly and carefully , "each person who works must pay part of his or her salary to the government . If you make a high salary , your taxes are high . If you don't make much money , your taxes are low ." "Is that clear ?" she asked . "Does everyone understand the meaning of income tax ?" The students nodded. "Are there any questions ?" she asked . The students shook their heads . "Very good !" she said . "Now ,I would like you to take a piece of paper and write a short paragraph on the subject of income tax ." Little Joey was a slow learner . He had lots of problems with spelling and grammar , but this time he at least seemed to understand the task . He took his pen and after a few minutes , he handed the teacher the following composition : Once I had a dog . His name was Tax . I opened the door and in come Tax .
Question: The teacher was trying to explain _ one day .
Options: (A) the basic principles of the income tax (B) how the government works (C) everyone should pay income tax (D) how much tax one should pay for his income
A