Few records related to toothpaste or powder then exist, until around 1000 AD when the Persians wrote to advise their people to be wary of the dangers1 of using hard abrasives as toothpowders.

现存的有关牙膏或牙粉的古时记录很少，直到约公元1000年才有波斯人的书面记载，提醒他们的人民提防用硬磨料做牙粉的危险。

youdao

Your goal should be to work very hard at one, then work at the other on an AD hoc, as-needed basis.

您的目标应当是在某一方面非常努力，然后另一方再根据需要改进。

youdao

"It's hard to sell ads when you don't have an audience," he said, and it's hard to build an audience without AD money flowing in.

他说：“当你没有受众时，很难卖得出广告，”而没有广告资金流入，又很难获得受众。

youdao

Republicans turned the remark into a hard-hitting television ad, contrasting it with comments from Americans expressing simple, unwavering faith in their country.

CNN: A First Lady of a different kind

The ad industry works so hard to keep faith out of the mix that is has backfired.

FORBES: What Role Does Faith Play in Building Brands?

Democrats waged a multimillion-dollar ad campaign and lobbied hard for the bill but still came up 13 votes short of the two-thirds needed to pass.

NPR: Mukasey Questioned on Torture