Answer:
He has used careless language.
Explanation:
Chuck has used careless language while a writing a letter to the teacher of a school.
Chuck replied to the letter of a teacher who had requested a company tour for his class student. He denied the teachers request of a company tour by using careless language and this may lead Chuck to legal difficulties.
Chuck could have been much more polite to the teacher.
Thus the answer is
"He has used careless language".