Explanation:

Why Option B is Correct?

In Vlocity (Salesforce Industries) Context Rules, a rule set is a container for one or more rules, but it does not require multiple rules to be valid. Key points:

A rule set can function with just one rule.

Example: A rule set named "Premium Customer Discount" might contain only one rule checking if Account.Type = "Premium".

Adding more rules is optional (e.g., to handle additional conditions like product categories or date ranges).

Why Option A is Incorrect?

While rule sets can hold multiple rules (e.g., for complex logic), it’s not mandatory.
The system does not enforce a minimum rule count.