When Is Learning of a Second Language Detrimental to the Development

When is learning of a second language detrimental to the development of a child?

A) If a child learns a second language after the age of 6, the second language will cause retroactive interference on use of the first language.
B) If a child learns two languages that are similar to one another, there will be a great deal of linguistic confusion as the child ages.
C) Learning of a second language is never detrimental.
D) If a child from a minority group is educated only in the language of the majority, it may undermine proficiency in the heritage language.