刚看到 gcp 网站上这么写的：
Your free trial credit applies to all GCP resources, except that you cannot:
Have more than 8 cores (or virtual CPUS) running at the same time.
Add GPUs or TPUs to your instances.
Request a quota increase. For an overview of Compute Engine quotas, see Resource Quotas.
You must upgrade your account to perform any of the actions in the preceding list.