When writing, you can most effectively use a dash to

Typically dashes are used to get the reader’s attention. They place an emphasis on certain words within a sentence. These words are often grouped together or require a pause when reading. If words within parentheses indicate lesser importance, a dash adds an indication of importance to words.

Dashes can be used in sentences to subsitute to a semicolon in which a distinguishing manner can be added in the structuring of the sentence. It is used in  enumeration in identifying things that are specified in the sentence. Answer then is B.