Which of the Following Students' Statement Is the Best Summary

Which of the following students' statement is the best summary of the research on bilingualism?

A) Nils: "Bilinguals have an advantage over monolinguals in their syntax,but not in their basic understanding of language."
B) Joe: "Bilinguals have advantages over monolinguals in many areas,such as metalinguistics and performance on cognitive tasks; they have slight disadvantages in a few areas."
C) Jorge: "Bilinguals have an advantage over monolinguals in terms of social skills concerned with language; however,when we look at proficiency in their first language,monolinguals have a better command of syntax."
D) Tanya: "So far,no major differences between monolinguals and bilinguals have been detected."