Which idea is developed throughout the selection?

Responses
A Linguists know the reasons English is difficult to learn.Linguists know the reasons English is difficult to learn.
B The names of many plural nouns in English are strange.The names of many plural nouns in English are strange.
C The origin story is the primary reason for English being difficult.The origin story is the primary reason for English being difficult.
D Languages evolve and change when people move. Languages evolve and change when people move.

C The origin story is the primary reason for English being difficult.