Select the strategies that help to lower the number of search results returned by a search engine or database. (there is more than one answer)

1. Using the + sign next to a word in the search field

2. Using quotation marks around specific words in the search field

3. Using - next to words in the search field

4. Using AND. OR, NOT in the search field

5. Typing a full question in the search field

6. Using keywords in the search field