Not necessary, because the reasoning relies on the previous club president’s decision regarding a tax accountant. The reasoning does not cite to other decisions by the club president.

Not necessary, because the reasoning has nothing to do with the expectations of members. Although the author does assume that the previous club president’s decision was appropriate, the propriety of this decision does not have to be related to what the members expected.

Not necessary, becauase the argument concerns whether the decision to invite Dr. Hines was appropriate. Whether the invitation was accepted is irrelevant.

Not necessary, because the reasoning does not depend on any difference between the current president’s discretion in hiring a speaker and the previous president’s discretion in hiring an accountant. Even if the club president has the same amount of discretion in hiring an accountant as in hiring a speaker, if the previous club president’s decision was appropriate, that can still constitute a reason to think the current club president’s decision was appropriate.

Necessary, because if it were not true — if the previous club president did NOT act appropriately in hiring the accountant without consulting members beforehand — then the author’s analogy is not persuasive. The previous club president’s action was inappopriate — it wouldn’t constitute a reason to think the current president’s decision was appropriate.