The principle defines public nuisance as an act causing common injury, danger or annoyance to the public, or likely to cause it, and adds that a common nuisance is not excused just because it also brings some benefit. A burns crop residue on his own farmland next to a residential area, and the smoke travels over the road and into nearby houses.
Since the smoke reaches a public road and multiple houses, causing common annoyance to people who have nothing to do with A's farming choices, the facts fit the principle's definition of public nuisance directly.
Therefore, the correct answer is A has committed public nuisance.
The fact that decides this question is where the smoke actually goes, it spreads over the public road and into houses in the neighbouring colony. Since the principle tests effect on the public rather than intent, ownership, or personal benefit, each option can be checked against that single spread of smoke.
Since the smoke's spread to a public road and multiple homes is the deciding fact, and none of the other three options actually address that spread, the option naming public nuisance is the one that fits.
Therefore, the correct answer is A has committed public nuisance.