Final answer:
Before the Green Revolution, large increases in crop production mainly resulted from synthetic fertilizers, irrigation, and selective breeding.
Step-by-step explanation:
The large increases in crop production before the Green Revolution were mainly the result of synthetic fertilizers, irrigation, and selective breeding. Synthetic fertilizers provided plants with essential nutrients, allowing them to grow faster and produce more crops. Irrigation ensured that plants had a consistent water supply, improving their growth and yield. Selective breeding involved choosing plants with desirable traits and breeding them together, leading to the development of high-yielding crop varieties.