Franz, the protagonist of the story "The Last Lesson" by Alphonse Daudet, was anxious as he entered the classroom due to the following reasons:

Fear of Punishment

Franz had not prepared for the French lesson and was afraid of being punished by his new teacher, M. Hamel. As he entered the classroom, he saw that the teacher was already there, looking very serious. This increased his anxiety, and he thought that he would be scolded for not being prepared.

Sense of Regret

Franz was also anxious because he had not taken his French lessons seriously before. He had always thought that he could learn the language later when he needed it. However, now he realized that it was too late, and he regretted not paying attention to his lessons earlier.

Feeling of Helplessness

Franz was also anxious because he knew that it was the last French lesson, and M. Hamel would be leaving the school. He felt helpless and sad, thinking that he would never be able to learn French again. He realized that he had taken the language and the teacher for granted and had not valued their importance until now.

Uncertainty of the Future

Franz was also anxious about the future of his country. He knew that the Prussians had taken over Alsace and Lorraine, and French language and culture were in danger. He felt that he had failed in his duty to learn his national language and to protect it from being erased by the Prussians.

In conclusion, Franz's anxiety as he entered the classroom was due to a combination of fear, regret, helplessness, and uncertainty. These emotions were a result of his realization that he had not valued his French lessons and his teacher until it was too late.