The correct answer is B) Method of air charging a cylinder and expelling exhaust gases. The number of events occurring in a cycle of operation in an internal combustion engine is determined by the method of air charging the cylinder and expelling the exhaust gases, not by the crankshaft revolution, the distance a piston travels, or the number of pistons. This is because the four-stroke cycle (intake, compression, power, exhaust) is the fundamental operating principle of most internal combustion engines, and this cycle is defined by the flow of air and exhaust gases through the engine. The other options are incorrect because they do not directly determine the number of events in the engine cycle. The crankshaft revolution, piston travel, and number of pistons are all important factors in the engine's operation, but they are not the primary determinants of the number of events in the cycle.