A cross-object formula field on the Case object is the most efficient and direct solution. Formula fields are calculated at runtime, ensuring the value displayed is always the real-time value from the parent Account record. Since the source field (Support Level) is a picklist, the TEXT() function is required within the formula to convert the picklist value into a text string that can be displayed on the Case record. This approach is declarative, requires no code or complex automation, and perfectly meets the requirement.

B. Create a formula field on the Account object using the ISPICKVAL function.

This is incorrect because the field must be on the Case object to display the data there. Additionally, ISPICKVAL is a boolean function that checks for a specific picklist value; it does not return the value itself.

C. Create a Process Builder and use a field update on the Case object.

While technically possible, this is not the best solution. It is not truly "real-time" as it relies on a trigger-like automation. It is also less efficient and more complex to maintain than a simple formula field for a display-only requirement.

D. Create a roll-up summary field using Support Level on the Account object.

This is incorrect. Roll-up summary fields aggregate data from child records onto a parent record in a master-detail relationship. This requirement is to display parent data on a child record, which is the opposite data flow.

1. Salesforce Help - Formula Field, Cross-Object Formulas: "A cross-object formula is a formula that spans two related objects and references merge fields on those objects... For example, you can write a cross-object formula to display the Account Name on a contact record." This principle applies directly to displaying an Account field on a Case.

Source: Salesforce Help, "Build a Formula Field," Section: "Tips for Building Formula Fields."

2. Salesforce Help - Formula Operators and Functions (TEXT): "Use TEXT to convert a picklist value to a Text value... For example, to display the text of a picklist field named SupportLevelc, use TEXT(SupportLevelc)."

Source: Salesforce Help, "Formula Operators and Functions," Section: "Text Functions."

3. Salesforce Trailhead - Formulas and Validations: "Cross-object formulas are formulas that span two or more objects by referencing merge fields." The module provides examples of pulling parent data (like Account fields) onto child records (like Contacts or Cases).

Source: Trailhead, "Formulas and Validations" module, "Use Formula Fields" unit.