Final answer:
President Trump's ban on immigrants from primarily Muslim countries led to legal challenges and nationwide protests against the policy, which was seen as discriminatory.
Step-by-step explanation:
One effect of President Trump's ban on immigrants from primarily Muslim countries was C) Legal challenges and protests. This ban, which targeted people from certain countries, sparked significant controversy and was met with a swift backlash. Various groups and individuals argued the ban was discriminatory and unconstitutional, leading to numerous legal challenges in US courts.
Additionally, there were widespread protests across the country, with people advocating for the rights of immigrants and against what they saw as a policy rooted in xenophobia and Islamophobia.