TOEFL Reading: ETS-TOEFL阅读机经 - KS74S3H70Y3S43L7L$

According to paragraph 6, large batches of clay writing tablets were stored because the tablets A. were being produced quickly and in large quantities B. did not serve any practical purpose for most Mesopotamians C. contained information that needed to be available for future reference D. could not be used again once they had been written on