The rate of use computer at your work :

4) completely100 % usage of computer

I think it is100% usage of computer in offices especially in mine. Most of the companies have deleted manual data registering on registers and ledgers.

Number4 every one is using the PC

Yes

4)100%

is the correct because ERP softwares 

4) completely _100 % is the rate using.

At my work use computer :4) Completely_100%