I would say that A is correct because if foreign born children were placed with younger children that were born in the country they thought they were equal intelligent to younger children.
C their is allot better, and next time run each word through the sentence.
Sub-questions are narrower questions. They are important because they provide the 'skeleton' around which you will find information to answer your main research question.
Auggie has had 27 surgeries since he was born.
