The mla style is one of three commonly used documentation formats.

true
false

The answer is: "TRUE".

The MLA (Modern Language Association) style is one of the 3 (three) commonly used documentation formats.

The other (2) of the most commonly used documentation formats are:

the APA (American Psychological Association); and 
the CMS (Chicago Manual of Style).

Of course, these are the three most common; there are many others, including:

the AAA (American Anthropological Association); 
the ACS (American Chemical Society); 
The AMA (American Medical Association); 
  and many more.