What does NIIS stand for?

The correct answer is 'Nonimmigrant Information System.' NIIS is specifically designed to manage and provide information related to nonimmigrant applications and statuses. This system plays a crucial role in tracking the various categories of nonimmigrant visas, ensuring that data regarding nonimmigrant entrants is organized and accessible, which is essential for processing applications and maintaining accurate records.

The other options, while they may sound plausible in the context of immigration systems, do not accurately capture the intended function or designation of NIIS. The phrase 'National Immigration Information System' suggests a broader scope that includes both immigrants and nonimmigrants, which does not align with the specific purpose of NIIS. The term 'Non-International Information System' incorrectly implies that the focus is on information beyond the scope of immigration, while 'National Internal Information Structure' does not relate to immigration at all. Hence, 'Nonimmigrant Information System' is the correct choice as it directly aligns with the operational focus of the system.