Noting that its network is vulnerable to attacks by internet hackers, the company has retained a team of information technology consultants to update network security, construct a new data storage facility, instructing employees on how to prevent the spread of computer viruses.

A instructing employees on how to prevent
B instructing employees for preventing
C and instruct employees for the prevention of
D and instruct employees on how to prevent
E instructing employees about preventing

OA is D
Can an Expert please give an explanation to buttress the OA?