Reading Comprehension - Endangered Languages

Read the following passage and answer the question that follows :

An endangered language is one that is likely to become extinct in the near future. Many languages are falling out of use and being replaced by others that are more widely used in the region or nation, such as English in the U.S. or Spanish in Mexico. Unless current trends are reversed, these endangered languages will become extinct within the next century. Many other languages are no longer being learned by new generations of children or by new adult speakers ; these languages will become extinct when their last speaker dies. Infact, dozens of languages today have only one native speaker still living, and that person's death will mean the extinction of the language : It will no longer be spoken, or known, by anyone. Ancient Greek and Latin languages are considered dead because they are no longer spoken in the form in which we find them in ancient writings. But they weren't abruptly replaced by other languages ; instead, Ancient Greek slowly evolved into modem Greek, and Latin slowly evolved into modem Italian, Spanish, French, Romanian, and other languages. In the same way, the Middle English of Chauceis day is no longer spoken, but it has evolved into Modern English

"These languages will become extinct ...." In the above sentence "these" refers to :

Spanish language evolved out of

What is endangered language ?