Select the most appropriate word to fill in the blank.

The unruly behaviour of the students ______ their teacher.

irritated

The most appropriate word to fill in the blank is irritated.

The word "irritated" means to make someone annoyed or angry. It is the most appropriate word to use in this context, as it conveys the meaning of the teacher being annoyed or angry by the students' unruly behavior.

The other options are not as appropriate.

• Pleased means to make someone happy or content. This is not the right word to use, as it does not make sense to say that the teacher was pleased by the students' unruly behavior.
• Comforted means to make someone feel better or less upset. This is not the right word to use, as it does not make sense to say that the teacher was comforted by the students' unruly behavior.
• Calmed means to make someone less excited or angry. This is not the right word to use, as it does not make sense to say that the teacher was calmed by the students' unruly behavior.