Option B is the most appropriate solution in this case. Mounting a Local SSD volume as the backup location will allow the backups to be taken quickly and efficiently, as Local SSDs have very high I/O performance and low latencies. Additionally, using gsutil to move the backups to Google Cloud Storage after they have been taken will provide a secure and durable storage location for the backups.
A, configuring a cron job to use the gcloud tool to take regular backups using persistent disk snapshots, may not be the most efficient option because persistent disks have relatively lower I/O performance compared to Local SSDs.
C, using gcsfuse to mount a Google Cloud Storage bucket as a volume directly on the instance and writing the backups to the mounted location using mysqldump, may not be the most efficient option because the backups would need to be transferred over the network, which could impact the performance of the backups.