Dombey's "heavy gold watch chain" and "trim blue coat" suggest that
a) he is a humble man of the people.
b) he once belonged to the military.
eliminate
c) he does not have many possessions.
d) he has achieved a measure of material success.

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.

the answer is somber