Final answer:
In a Knowledge Management Service Portal, 'Most Helpful Articles' typically refers to the articles that users have marked as helpful at the highest rate, indicating valuable content.
Step-by-step explanation:
In the context of a Knowledge Management Service Portal, the items that display articles with the highest percentage of users marking them helpful are typically referred to as D) Most Helpful Articles. These are the articles that have been rated by users as being the most useful in resolving their queries or providing the information they needed. Different Knowledge Management systems may have varying names for this category, but the underlying idea is to highlight content that has proven to be valuable to a large proportion of users, thus facilitating easier access to high-quality, helpful information.