He imparted his discoveries to the English brewers as well as to French.

Explanation

"French" is missing the definite article "the." It should be "the French" to parallel the structure of "the English brewers." There is an error here.The error in the sentence is the omission of the definite article "the" before "French." The correct phrase should be "to the French." Thus, the correct option to mark the error is D) French.