Which of the following lines from "True Stories of History
and Biography" uses a tone
that reveals Hawthorne's
attitude toward Isaac
Newton?
A. in 1727, when he was fourscore and
five years old
B. Sir Isaac Newton died, --or rather, he
ceased to live on earth
C. On Christmas day, in the year 1642,
Isaac Newton was born

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 feel like it is actually b.