Final answer:
The agricultural revolution in Britain was primarily triggered by crop rotation techniques, the seed drill, and selective livestock breeding. These practices vastly improved agricultural productivity and efficiency.
Step-by-step explanation:
The three inventions that helped trigger the agricultural revolution in Britain were crop rotation techniques, the seed drill, and selective livestock breeding. Crop rotation, a practice dating back to around 8000 BCE, enhanced soil fertility and thereby increased yields.
The seed drill, a device introduced in the Industrial Revolution, allowed for the efficient planting of seeds in well-spaced rows at specific depths. This increased the germination rate and yield per acre. Selective breeding of livestock improved animal traits, leading to higher-quality meat, milk, and wool production.
The other options given, railroads and the electric lightbulb, although significant in their respective fields, were not direct triggers of the agricultural revolution in Britain.