Using the Boolean Operator "AND" to Connect Two Words Has

Using the Boolean operator "AND" to connect two words has what effect on the results of a keyword search of a literature database?

A) It expands the results to include all articles containing either word.
B) It narrows the results to include only articles that contain both words.
C) It limits the results to include only articles where the two words appear side by side in phrases.
D) It defines the search results by one or the other word.