As stated in the description of the Colonial Pipeline ransomware attack

Question $9$ options:

a$)$

The attack was caused because an employee accidentally gave away his or her password

b$)$

The attack was caused because an employee didn't use a VPN on his or her smartphone

c$)$

The attack was caused because the attackers sent a worm to Colonial

d$)$

The attack was caused because Colonial left an unused VPN device connected to their system