In Terms of Digital Data Stored on a Computer, What

Multiple Choice

In terms of digital data stored on a computer, what is an extension?

A) A set of numbers that occur at the beginning of a file name which specify when the file was created
B) The three-to-six character ending to a file name which specifies what type of file it is
C) Any software upgrade that extends the lifetime of a program on the computer
D) Extra storage space for files