In the following question, some part of the sentence may have errors. Find out which part of the sentence has an error and select the appropriate option. If a sentence is free from error, select "No Error".
His reputation for(A)/being rough on(B)/students was well earned.(C)/No error(D)

The sentence "His reputation for being rough on students was well earned." is grammatically correct and idiomatic. The preposition "for" correctly follows "reputation", "being rough on" is the correct phrasal usage meaning harsh toward someone, and the singular verb "was" agrees with the singular subject "reputation". Thus, there is no error.