Elephants, the largest mammal on earth ,since it's through their feet won't warning from other elephants up to 20 miles away

yes, they are. i think.

type of error:

the error in the sentence is a "dangling modifier". a dangling modifier is a phrase, word or clause that "dangles" because there is not target to modify. in this case, "after mopping the floor" is the dangling modifier since it has no word to modify. the noun "house" cannot mop the floor; therefore there is a mistake in the writing of the sentence.

i think idk if im right but i think its d