短语讲解：

1.So, an increasing number of American schools are requiring students learn about these documents before they can graduate.

learn about 获得，学得; 得知有关…的消息
例句：He was deeply grieved to learn about his teacher's death.
他得知老师去世的消息，非常难过。

2.Since 2012, Kentucky, Arkansas and at least 12 other states put into effect such requirements.

at least 至少
例句：He's been away for at least a week.
他走了总有一个星期吧。
put into effect 实施; 实行; 使生效; 实现
例句：The bill was put into effect last month.
那法规于上个月生效。

3.Others are worried about the way Republican President Donald Trump and his supporters use their power.

worry about 担忧， 烦恼; 惦念
例句：Don't worry about him; he is a cheerful and elastic man.
别为他担心;他是个快活开朗的人。

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