What is the purpose of "export" when used with a variable in bash, e.g. "export VAR=value"?

A It marks the variable as an "environment variable" that will be inherited by child processes spawned from the current shell, as opposed to a regular shell variable which is local to the current shell only B It permanently writes the variable to disk so it survives a reboot C It deletes the variable after first use D It converts the variable into a read-only constant