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網絡上看到B-2的是住在外國的美國公民（美僑）領養的孩子。至今還沒有看到樓主的情況可以用B-2.
-Here are a couple of examples:
http://www.alanleelaw.com/english/qa/QA2013-11-10.html
http://www.avvo.com/legal-answers/us-citizen-parent-adopted-child-from-india--she-en-453426.html

這個文件說綠卡在本國領養孩子可能來不了。
http://travel.state.gov/content/adoptionsabroad/en/adoption-process/who-can-adopt/adoptions-by-non-us-citizens-living-in-the-us.html
-It seems that is related to that the adopted child can not immigrate to join the adopting parents (green card holder) immediately after adoption. The B-2 visa is for regular people including the adopted child. Of course, whether the B-2 application is approved or not is up to the visa officer's decision, and this applies to all the B-2 visa applicants (not special to the adopted child). As long as the adopted child shows the visa officer the purpose of the travel is to accompany the adopting parents for a temporary visit, he/she will be offered the B-2 visa. There is not specific period of time  to define the "Temporary", and it may be a few months or a couple of years (extension application may be needed within US).

Here is the related rules for B-2 visa for a adopted child at: 
http://www.americanlaw.com/b-2.html

Notes 10 and 11 to §41.31 of the DOS Foreign Affairs Manual ("FAM") , the manual used by United States consulates located abroad: 
........
N11.3.--Spouse or Child of U.S. Citizen or Resident Alien. An alien spouse or child, including an adopted alien child, of a United States citizen or resident alien may be classified as a nonimmigrant B-2 visitor if the purpose of the travel is to accompany the spouse or parent for a temporary visit.