The error is in part (A) "Having received no reply to his call." The phrase "his call" creates ambiguity - whose call is being referred to? If it's the teacher's call, then logically the teacher would be criticizing students for not responding. However, the context suggests the teacher is criticizing students' attitude toward studies, not their lack of response. The sentence structure makes it unclear whether "his" refers to the teacher or someone else. A clearer phrasing would be "Having received no reply to his repeated reminders" or "their lack of response."