Which of the following is a valid DML operation through the SOAP API?

The valid DML operation through the SOAP API is the merge() function. This operation is specifically designed to combine two or more records into a single record, effectively maintaining the data integrity while allowing the user to retain relevant information. This is particularly useful in scenarios where you have duplicate records in Salesforce and wish to consolidate them into one.

The merge operation is part of the standard functionality provided by Salesforce’s APIs, allowing for efficient data management. It helps avoid data redundancy and maintains a clean database, which is crucial for ensuring accuracy in reporting and data analysis.

The other options do not represent valid DML operations within the context of the SOAP API. For instance, append() and detach() are not recognized DML operations as defined by Salesforce, indicating that they cannot be utilized for managing records through the API. Similarly, fetch() does not align with the operations available through the SOAP API, as it typically pertains to retrieving data rather than modifying it.