A. IF(NOT(ISBLANK(Nickname__c)),Nickname__c,FirstName) The formula "IF(NOT(ISBLANK(Nickname__c)),Nickname__c,FirstName)" checks if the "Nickname__c" field is not blank. If it is not blank, it returns the value in the "Nickname__c" field, otherwise it returns the value in the "FirstName" field. This formula allows the app builder to select the contact's preferred name, whether it is stored in the "Nickname__c" field or the "FirstName" field.

A is correct, it's tested

A is correct.

A is correct but D is the best option for the scenario. Handling Null Values: BLANKVALUE handles both null values and blank values, whereas ISBLANK specifically checks if the field is blank (empty string, whitespace) but doesn't handle null values. In practical scenarios, null values might exist, especially in custom fields that are not required. BLANKVALUE ensures that if the field is null, it still behaves as expected, providing a default value. This makes option D more robust in handling various scenarios. Although both options A and D could achieve the desired outcome, option D (using BLANKVALUE) is preferred due to its ability to handle null values, improved readability, consistency, and potential performance benefits.