Ответ:

Articles: 1 a pencil sharpener; 2 a ruler; 3 a rubber; 4 a pencil case; 5 a notebook; 6 an atlas; 7 a blackboard; 8 a book; 9 a school bag; 10 a pen; 11 a pencil; 12 a notepad; 13 a timetable.

The article a is used before a consonant sound; an is used before a vowel sound.

Example dialogue: What's this in English? — It's an atlas.