Which of the following commands gets the GnuPG public key with the id 63B4835B from the keyserver ? example.com

The `gpg` command with `--keyserver hkp://example.com` correctly designates the keyserver using the HTTP Keyserver Protocol. The `--recv-key 63B4835B` option is the specific GnuPG subcommand used to fetch a public key by its identifier and add it to the local keyring.

The `--search-key` option is used to search for keys, not directly receive a specific key, and the syntax `[email protected]` is incorrect for specifying a keyserver and key ID for retrieval.

The `--get-key` option is not a standard GnuPG subcommand for retrieving keys from a keyserver, and `gpg://` is not the standard protocol used for keyservers.

The `--add-key` option is not a standard GnuPG subcommand for retrieving keys from a keyserver; it usually pertains to importing local keys, and the syntax is incorrect for fetching from a server.

The `--key` option is not a standard GnuPG subcommand for retrieving keys from a keyserver, and `gpg://` is not the recognized protocol for keyserver communication.