Final answer:
A common home network password mistake is using the default passwords that come with routers, as they are easily exploitable by hackers.
Step-by-step explanation:
One of the common mistakes people make with home network passwords is D) Using default router passwords. Many users fail to change the default password that comes with their router, which can be a serious security risk. Default passwords are often well-known and can be easily found by malicious actors looking to gain unauthorized access to a network. It is essential to set a strong, unique password for your home network to protect your devices and personal information from cybersecurity threats.