"На третий день подъем по снежной равнине сделался более заметным и появилось больше трещин, которые замедляли движение. " - Не понимаю, почему отсутствует запятая после союза "и"?

Обьясните наличие или отсутствие артикля перед существительными.

 1. Last week I met my friend. He was with a young girl.The girl was a student of our Academy.2. This is a pencil. The pencil is red. 3. She is a teacher. She is our teacher of English. 4. It is a lake. The lake is deep. It is one of the deepest lakes in the world. 5. There are many flowers in your garden. The flowers are beautiful. 6. Did you write the plan? Give me please your plan. 7. The Black Sea is in the South of Russia. 8. This is Nick. He is an engineer. He is a good engineer. 9. There are some schools in our street. The schools are new.10. Yury Gagarin was the first cosmonaut of the world. 11. In summer the sky is blue and the sun shines brightly. 12. The Petrovs are very friendly. 13. This is Ann`s book. 14. Winter begins in December.