The word "obscurity" in paragraph 2 could best be replaced by ______.

A．Words and phrases accepted by the majority for formal usage.
B．Words and phrases understood by the majority but not found in standard dictionaries.
C．Words and phrases that axe understood by a restricted group of speakers.
D．Words and phrases understood by a large number of speakers but not accepted as formal usag

A．Standard speech.
B．Idiomatic speech.
C．Different types of speech.
D．Dictionary usag