Теория:

Study information about the definite article.
 
We use the in these situations:
 
1. nouns are unique.
 
Haven't you been to the Acropolis yet?
  
acropolis-2725910_640.png
Рис. \(1\). The Acropolis
 
2. names of cinemas, museums, hotels, theatres, newspapers, ships.
 
I want to go to the National Gallery.
  
united-kingdom-89977_640.png
Рис. \(2\). The National Gallery
 
3. names of rivers, seas, groups of islands/states, mountain ranges, deserts, oceans.
 
The Thames is the longest river in England.
  
big-ben-2393098_640.png
Рис. \(3\). The Thames
 
4. names with of.
 
The Tower of London is the most wonderful sight.
  
5. musical instruments.
 
Can you play the piano?
  
piano-3505109_640.png
Рис. \(4\). The piano
 
6. names of people/families/nationalities in the plural.
 
The English are considered to be reserved.
 
7. titles without proper names.
 
The Queen, the President
  
queen-63006_640.png
Рис. \(5\). The Queen
 
8. adjectives used as plural nouns.
 
the rich, the poor
 
9. the superlative degree of adjectives/adverbs.
 
She is the friendliest person I've ever met.
  
man-3803551_640.jpg
Рис. \(6\). Friendly  
 
10. when it is clear which thing or person we mean.
 
Can you tell me the time, please?
Источники:
Рис. 1. The Acropolis, 2017, https://pixabay.com/images/id-2725910/ Pixabay License CC0 Free for commercial use No attribution required
Рис. 2. The National Gallery, 2006, https://pixabay.com/images/id-89977/ Pixabay License CC0 Free for commercial use No attribution required
Рис. 3. The Thames, 2017, https://pixabay.com/images/id-2393098/ Pixabay License CC0 Free for commercial use No attribution required
Рис. 4. The piano, 2018, https://pixabay.com/images/id-3505109/ Pixabay License CC0 Free for commercial use No attribution required
Рис. 5. The Queen, 2012, https://pixabay.com/images/id-63006/ Pixabay License CC0 Free for commercial use No attribution required
Рис. 6. Friendly, 2018, https://pixabay.com/images/id-3803551/ Pixabay License CC0 Free for commercial use No attribution required