The following sentence is punctuated properly: "I need to know whether you are able to perform the following functions of the job: revising existing marketing materials, promoting the company at trade shows, and reaching potential customers through direct mail campaigns." (3).
There should be a colon after the first clause because the second part of the sentence is a list of items (in this case, a list of the "functions of the job").
A comma would be too weak in this case because it would fail to express this idea of a list of specific examples completing the independent clause.
A semicolon would be inaccurate because they are usually used between two independent clauses when you don't want to link them with a conjunction (like <em>and</em>). They are stronger than a comma and weaker than a period. In this sentence however, the second part is not an independent clause but a list without a verb.
