以前读MBA学税法知道dependent有resident test

刚才又去查了一下2006年publication 501, 这里是copy的有关段落，

也许我理解有误？哪位知道的解释一下，谢谢。
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You can claim an exemption for a qualifying child or qualifying relative only if these three tests are met

1. Dependent taxpayer test.
2. Joint return test.
3. Citizen or resident test.


Citizen or Resident Test：
You cannot claim a person as a dependent unless that person is a U.S. citizen, U.S. resident alien, or a resident of Canada or Mexico, for some part of the year. However there is an exception for certain adopted children as explained next.