Which one of the following is true about word processing, spreadsheet and presentation software?单项选择题

a. These are all computer programs that store user input in the form of separate files sometimes referred to as data files.

b. These applications are actually utility programs because they enable the user to work more effectively and efficiently.

c. These programs are applications that are in the form of executable files, which form the most important part of any operating system.

d. These are called applications because the provide instructions to the CPU on how to control and manage the hardware.