The Azure portal is the correct answer because Azure Cloud Shell can be directly accessed by selecting the Cloud Shell icon within the Azure portal interface. This is explicitly mentioned in the Microsoft documentation referenced in the community discussion and confirmed by multiple commenters with high upvotes. While Azure Cloud Shell provides access to Azure CLI and Azure PowerShell environments once launched, these are not the tools used to start Cloud Shell itself. Similarly, ARM templates are used for infrastructure deployment, not for launching Cloud Shell. The community consensus strongly supports option A with 100% agreement across all responses.