Answer:
The advantages of the internal combustion engine is that it is:
* Cheap
* High power to weight ratio
* It is possible to raise the efficiency to relatively high levels by minor means
* Emissions are minimized by advanced combustion control, design and aftertreatment. The only emission that can't be reduced by aftertreatment is carbon dioxide, here advanced control and new technology come in to play. In fact, atmosphere background emissions can very well be higher than those coming out of the tailpipe (carbon monoxide/unburned hydrocarbons).