Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
Trả lời câu hỏi dưới đây:
In some countries, on moral that education should not be taxed, there is no tax on books.
A. nguyên tắc
B. ý tưởng
C. nội dung
D. nguyên nhân