The section on Search Strategies $-$ Connecting Keywords outlines the use of Boolean operators. Which of the following is NOT a Boolean operator?

Question $8$ options:

a$)$

using IF when you are not sure if the concept is related

b$)$

using OR to combine synonyms and related terms

c$)$

using NOT to exclude a concept or word from the search

d$)$

using AND between keywords so that both terms must appear in the search results