Which is used in the rear of the tractor transmission part for attaching the combine harvester, mower, thresher, etc. to the tractor?

Correct option is A

PTO (Power TakeOff) is a mechanical device that is used in the rear of the tractor’s transmission.
It provides a means for transmitting power from the tractor to various implements and machinery attached to it. The PTO is commonly used for connecting and powering equipment such as combine harvesters, mowers, threshers, and other implements.
The PTO allows these machines to be mechanically driven by the power generated by the tractor’s engine. It typically involves a rotating shaft that extends from the tractor, and this shaft can be connected to compatible equipment using a PTO driveline.