1. Вставь: a or an. 1 ... atlas 2 ... pen 3 ... timetable 4 ... apple 5 ... school 6 ... orange.

an atlas 2. a pen 3. a timetable 4. an apple 5. a school 6. an orange.

A / an is indefinite article. We use indefinite article with singular and we don't use indefinite article with plural. The meaning of indefinite article is one. A is used before consonants and an is used before vowels.