What type of language convention has the author used to separate the declarative sentence from the disruptive phrase in this excerpt from "totally like whatever, you know? "

"declarative sentences—so--called
because they used to, like, declare things to be true, okay,
as opposed to other things are, like, totally, you know, not—
have been infected by a totally hip
and tragically cool interrogative tone? "

commas

question mark

capitalization

em dashes

The language convention that the author has used to separate the declarative sentence from the disruptive phrase in this excerpt from "Totally like whatever, you know" are the em dashes.
The disruptive phrase is something that doesn't quite belong there, and should be moved to other parts of the sentence so as not to disrupt the natural flow. Here, the disruptive element is set off from the rest of the sentence using em dashes: so--called because they used to, like, DECLARE things to be true, okay, as opposed to other things are, like, totally, you know, not.

These objects represent mayan numerals. just like roman numerals, they are combined to symbolize a numeral and this enabled astronomers, scholars and architects to compute various equations yet it was also used by farmers and traders in their day to day transactions.

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