Question:
is less than the 21-year-old, unmarried children of immigrants to the United States to visit his mother the kind of visa.

Answer:
v visa is a United States immigrant visa category of “special immigrant visa families.”
as a priority by the U.S. immigration visa immigration legal permanent resident spouses and minor children (under 21 years of age), with United States immigration laws and in accordance with the V visa eligibility.
the applicant must be at least three years in the U.S. immigrant visa to apply for their children V-immigrant visa category.

Answer:
the United States to the United States V visa is a permanent resident (green card holders are not U.S. citizens) the spouse or unmarried children under the age of 21, the temporary visas for these people prior to obtaining a green card to the United States and their relatives reunion.

Answer:
to the visa officer must provide proof of the child to return home. To avoid migration.2008-07-25
问题:
就是给不到21岁，未婚的孩子到美国看望移民母亲的那种签证。

回答:
v签证是属于美国的移民签证类的“家庭移民特殊签证”。
被美国移民局列为优先移民签证的合法{yj}居民的配偶和未成年子女（21岁以下），具有和符合美国移民法的V签证资格。
申请人必须是在美国至少三年的移民签证，才能申请其子女V类移民签证。

回答:
美国V签证是给美国{yj}居民（绿卡持有人，不是美国公民）的配偶或者未婚21岁以下子女的临时签证，用于这些人在获得绿卡之前到美国和亲人团聚。

回答:
必须给签证官提供孩子能够回国的证明。避免移民。2008-07-25