The correct option is B Portable Document Format
PDF stands for Portable Document Format. Essentially, the format is used when we need to save files that cannot be modified but still need to be easily shared and printed. Today almost everyone has a version of Adobe Reader or other program on their computer that can read a PDF file. Documents that are portable-document formatted, end with ".pdf". extension. E.g. a document named variable_names.pdf indicates that it is a PDF document with the name variable_names.