下列语句的执行效果是（）
revoke create on schema public from public；

A.$user"，public
B.postgres"，public
C.test"，public
D.schema"，public

A.alter database db_name rename to newname;
B.alter database db_name owner to newname;
C.alter database db_name set tablespace new_tbspace;
D.alter database db_name reset all;