Maybe try looking it up or ask ur teacher for help
Immigration law is very complex, and there is much confusion as to how it works. The Immigration and Naturalization Act (INA), the body of law governing current immigration policy, provides for an annual worldwide limit of 675,000 permanent immigrants, with certain exceptions for close family members. Lawful permanent residency allows a foreign national to work and live lawfully and permanently in the United States. Lawful permanent residents (LPRs) are eligible to apply for nearly all jobs (i.e., jobs not legitimately restricted to U.S. citizens) and can remain in the country even if they are unemployed. Each year the United States also admits noncitizens on a temporary basis. Annually, Congress and the President determine a separate number for refugee admissions.
The answer is: b. The Soviet Union fell apart
Before Gorbachev's reforms exist, several territories in soviet union was united under one principle of communism.
When the Gorbachev's reforms were created, the soviet union started to adopt some of democratic and free market value that adopted by countries in western hemisphere.
When this happen, the bind that united territories in the soviet union no longer exist. This became one of the factors that caused the soviet union to fell apart.
They are territory of the United States, but not considered a state.