Final answer:
In MLA format, you underline titles of long works and place shorter works in quotation marks.
Step-by-step explanation:
In MLA format, you underline material when you are referring to titles of long works such as books, films, and plays.
For example, if you are writing an essay and you mention the title of a book, it should be underlined. However, shorter works such as articles, poems, and short stories are placed in quotation marks.