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课程多端同步更新，充分利用零碎时间。做题
海量精选试题，想练就练，瞬间提分。答疑
网校名师24小时在线答疑解惑。直播
名师大咖面对面，有问有大收获多。Thus the optimistic， "fair exchange" principle most likely started in Germany and was brought here by German immigrants. It was only left to America to replace the beneficent “tooth rat” with the more agreeable fairy and to replace the traditional hope of hard molars with our more characteristic hope of hard cash.
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