Final answer:
French had the greatest influence on the transition from Old English to Middle English, especially after the Norman Conquest of 1066.
Step-by-step explanation:
The Romance language that had the greatest influence on the shift from Old English to Middle English is French. This influence began after the Norman Conquest of 1066 when the Norman French became the language of the ruling elite in England. A significant number of French words entered the English vocabulary, and over time, these contributions heavily influenced the evolution of English from its Old to Middle form. The mix of Norman French with the existing Germanic-based Old English gave rise to Middle English, reflecting a melding of linguistic influences.