Definition: The subject of the conclusion talks about all of something, but the premises only refer to some of them.
The subject term of the conclusion refers to all members of that category, but the same term in the premises refers only to some members of that category.
Show that there may be other members of the subject category not mentioned in the premises which are contrary to the conclusion. For example, from (i) above, one might argue, "While it's true that all communists are critics of capitalism, it is also true that Thomas Jefferson was a critic of capitalism, but Thomas Jefferson was not a subversive, so not all critics of capitalism are subversives." Copi and Cohen: 208