The correct answer is A. Hashing, because hashing is specifically designed to verify file integrity and detect whether a file has been altered after its original creation or distribution. A hash is a fixed-length value generated by running a file through a hashing algorithm such as SHA-256 or SHA-1. Even a single-bit change in the file will produce a completely different hash value.
According to the Quentin Docter – CompTIA A+ Complete Study Guide, hashing is commonly used to validate downloaded software by comparing the calculated hash of the downloaded file with the hash published by the vendor. If the two values match, the technician can be confident that the file has not been modified or tampered with.
The Travis Everett & Andrew Hutz – All-in-One Exam Guide emphasizes that hashing ensures integrity, not confidentiality or authentication. SSL certificates secure data in transit, but they do not validate files after download. Plug-ins and extensions provide additional browser functionality but have no role in verifying file integrity.
The Mike Meyers / Mark Soper Lab Manual reinforces that hashing is a standard best practice in secure software deployment and malware prevention. It allows technicians to confirm that files are exactly as the publisher intended.
Because the requirement is to confirm that files have not been modified, hashing is the correct and most reliable method, making A the correct answer.
