What was a positive effect of immigration to the United States?
A. Immigrants to the United States consumed resources faster than resources could be renewed.
B. Some of the great contributors to advancement in the United States were immigrants.
C. Cultural conflicts arose due to the vast number of immigrants from different parts of the world.
D. The arrival of millions of immigrants to the United States resulted in poor living conditions.

The United States is a country of immigrants, so using the term immigrants for people that moved slightly later in the country is kind of debatable. Anyway, the later immigrants in the United States had a huge impact on the country, mostly positive.

The immigrants provided extra labor force which was in high demand, especially with the industry constantly growing.

Numerous immigrants were people with great ideas, managing to invent new things that led to a rapid development of the United States and making them a global power. A prime example of this is the Croatian Nikola Tesla.

The large numbers of immigrants resulted in rapid population increase, which also provided the United States with extra military power, which was crucial for its survival, interests, and further actions.