The most accurate response regarding how immigration to the U.S. has changed over time is:
Immigration to the U.S. was previously mostly from Europe and based on a quota system. Now, immigration to the U.S. uses a criteria system that places priority on reuniting families and bringing in skilled workers.
This response correctly reflects the historical context of U.S. immigration policy, highlighting the shift from a quota system that primarily favored European immigrants to a more criteria-based system that prioritizes family reunification and skilled workers.