All the evidence so far gathered fits both Dr. Grippen's

All the evidence so far gathered fits both Dr. Grippen's theory and Professor Heissman's. However, the predictions that these theories make about the result of the planned experiment cannot both be true. Therefore, the result of this experiment will confirm one of these theories at the expense of the other.

The argument above exhibits an erroneous pattern of reasoning most similar to that exhibited by which one of the following?

(a)Dave and Jane both think they know how to distinguish beech trees from elms, but when they look at trees together they often disagree. Therefor, at least one of them must have an erroneous method.

(b) Although David thinks the tree they saw was a beech, Jane thinks it was an elm. Jane's description of the tree's features is consistent with her opinion, so this description must be inconsistent with David's view.

(c) David and Jane have been equally good at identifying trees so far. But David says this one is an elm, whereas Jane is unsure. Therefore, if this tree turns out to be an elm, we'll know David is better.

(d)David thinks that there are more beeches than elms in this forest. Jane thinks he is wrong. The section of the forest we examined was small, but examination of the whole forest would either confirm David's view or disprove it.

(e) David thinks this tree is a beech. Jane thinks it is an elm. Maria, unlike David or Jane, is expert at tree identification, so when Maria gives her opinion it will verify either David's or Jane's opinion.

OA and OE will follow after the discussion