Select the most appropriate option to fill in the blank.

His ______ of the topic was so good that students had few doubts at the end of the class.

exposition

The correct answer is exposition.

The word exposition means a detailed explanation or presentation of something. In this sentence, the speaker is saying that the teacher's explanation of the topic was so good that the students had few doubts at the end of the class.

The options qualification, exhibition, and picturisation are not as appropriate because they do not have the same meaning as exposition. For example, the option qualification means a quality or skill that makes someone suitable for a particular job or activity, but this is not the same as explaining something in detail. The option exhibition means a public display of works of art, but this is also not the same as explaining something in detail. The option picturisation means the act of representing something in pictures, but this is also not the same as explaining something in detail.