Franz, the protagonist of the story "The Last Lesson" by Alphonse Daudet, noticed something unusual in his school that day. The correct answer is option 'A', which states that he noticed quietness in the school.

Franz noticed that the usual noise and commotion of the school were absent that day. There was a strange silence that hung in the air, which caught the attention of the young boy. This silence was unusual because the school was usually filled with the sounds of students chattering, moving desks, and teachers giving instructions.

Franz's observation of the quietness in the school is significant because it foreshadows the impending event that will change his life and the lives of his fellow classmates. The silence represents the absence of the usual hustle and bustle of the school, indicating that something out of the ordinary is happening.

The absence of noise also creates a sense of tension and anticipation in the story. It sets the stage for the revelation that the French language, which was previously taught in the school, would no longer be allowed. This news comes as a shock to Franz and his classmates, as they were not adequately prepared for such a drastic change.

The quietness in the school also serves as a symbol of the loss of cultural identity and the suppression of the French language. The invading Prussian soldiers have imposed their language and culture on the school, forcing the students to learn German instead. The silence in the school represents the erasure of French culture and the imposition of a foreign language.

In conclusion, Franz notices the unusual quietness in the school, which serves as a foreshadowing of the significant event that will disrupt his education and change the course of his life. The silence symbolizes the loss of cultural identity and the imposition of a foreign language.