Right option is (c) 30°
For explanation: The tractor shall be put on a level ground. The air cleaner should be cleaned and filled with normal oil. The engine shall be operated at full governed speed for 15 minutes with continuous acceleration and deacceleration. If there is no oil pull over with the tractor in level position the tests shall be repeated with tractor tilted 15° to either side and then 30° forward and backwards with direction of travel.