Final answer:
The standard format for digital certificates is X.509, which defines how certificates should be structured, tying public keys to entity identities. .cer is a file extension for certificate files, while JPG and MPEG-4 are unrelated image and multimedia file formats.
Step-by-step explanation:
The standard format for digital certificates is a. X.509. This is a widely adopted standard that outlines the format for public key certificates, which are used to associate a public key with an entity (usually a person or organization). The X.509 standard defines what information the certificate should contain and how that information should be structured. It's part of the X.500 series of standards for electronic directory services.
Option b. .cer refers to a file extension for files containing digital certificates. While related, it's not a format specification, but rather a file format that can hold X.509 certificates. Options c. JPG and d. MPEG-4 Part 14 are formats for digital images and multimedia files, respectively, and are not related to digital certificates.