The Study in Which People Who Immigrated to the United

The study in which people who immigrated to the United States at various ages were compared in terms of their ability to understand English grammar found that

A) age of arrival had no effect on mastery of grammar.
B) those who immigrated as children understood grammar as well as native speakers.
C) those who immigrated as adults understood grammar as well as native speakers.
D) whether or not English was spoken in the home was the most important factor in mastering the rules of grammar.