The correct answer is (i) and (iii).
The output of a bulldozer is the amount of work it can do in a given amount of time. The drawbar horsepower of the tractor is the power that is available to pull the bulldozer. The hauling distance is the distance that the bulldozer must travel.
If the drawbar horsepower of the tractor is increased, the bulldozer will be able to pull more weight. This means that it will be able to do more work in a given amount of time. Therefore, the output of the bulldozer will increase.
If the hauling distance is increased, the bulldozer will have to travel further. This means that it will take longer to do the same amount of work. Therefore, the output of the bulldozer will decrease.
Option (ii) is incorrect because the output of the bulldozer will increase if the drawbar horsepower of the tractor is increased. Option (iv) is incorrect because the output of the bulldozer will decrease if the hauling distance is increased.