What does Lexicology, a brunch of linguistics study?

What is the main way of enriching and enlarging the English vocabulary?

1. 
   *The main way of enriching the English vocabulary is word-building.
   
2. 
   The main way of enriching the English vocabulary is affixation.
   
3. 
   The main way of enriching the English vocabulary is conversion.
   
4. 
   The main way of enriching the English vocabulary is composition.
   
5. 
   The main way of enriching enlarging the English vocabulary is contraction.
   

9. 
   What do we mean by derivation?
   

1. 
   It is a structural type of Modern English words.
   
2. 
   It is a process of developing English words.
   
3. 
   * It is one of the most productive ways of word-building.
   
4. 
   It is a way of forming a new meaning.
   
5. 
   It is a process of producing a new sounds.
   

10. 
    Which categories of parts of speech are especially affected by conversion?
    

1. 
   The three categories affected by conversion are verbs, nouns and adverbs.
   
2. 
   The category of parts of speech affected by conversion is nouns.
   
3. 
   The category of parts of speech affected by conversion is verbs.
   
4. 
   *The two categories of speech affected by conversion are nouns and verbs.
   
5. 
   All categories of parts of speech are affected by conversion.
   

11. 
    Metaphor, metonymy, hyperbole are....
    

1. 
   types of grammar change.
   
2. 
   types of literary change.
   
3. 
   *types of semantic change.
   
4. 
   types of general change.
   
5. 
   types of morphological change.
   

12.