In the 3rd paragraph, "... in the regions where it could be practiced... ", here, "it" refers to ______.

A．positive
B．negative
C．not stated
D．indifferent

A．speech, agriculture and writing are the most important factors
B．the origin of the language can not be traced
C．both oral language and written language come out of the picture language
D．the ape might be taught to master speech