Final answer:
A former member of KP.org can sign into and use its features for 6 months after their membership has been terminated (option b).
Step-by-step explanation:
After the termination of membership, a former member has limited access to KP.org. The correct answer to how long a former member can sign into and use the features of KP.org after their membership has ended is: b) 6 months. During this period, the former member still can view their past health records and utilize some features before their account access is fully terminated.
Hence, the answer is option b.