Final answer:
Nitro shooting is the correct answer as it was the primary well stimulation method used during the 1860's to the 1940's. This method involved using nitroglycerin to enhance oil production, predating the widespread use of hydraulic fracturing.
Step-by-step explanation:
The well stimulation method used from the 1860's to the 1940's is Nitro shooting. This technique involved the use of nitroglycerin to break apart the producing formation and stimulate the flow of oil. It was one of the earliest methods to enhance production before more modern techniques such as hydraulic fracturing were developed. Hydraulic fracturing, often called fracking, is a method utilized to recover gas and oil from shale and other tight formations by injecting high-pressure fluids to create fractures in the rock. Although hydraulic fracturing has been known since the late 1940s, it wasn't used commercially until later, making Nitro shooting the correct answer for the time period in question.