What is the usual way to gain command line access to computing instances in an IaaS cloud?

What is the usual way to gain command line access to computing instances in an IaaS cloud?
A . By providing a public SSH key to the cloud management system and using the matching private SSH
key to log into the instances.
B . Usually computing instances are accessed through a web frontend and do not allow command line access.
C . By either telnet or SSH using the credentials of the cloud management system account with administrative privileges.
D . By using a telnet session with the credentials set and publicized by the creator of the computing instance’s system image.
E . By using a VNC console which does not require authentication when it is invoked via the cloud management system.

Answer: A