Mismatched premises. Like the stimulus, (A) establishes only two options (Johnson and Ringwold) for a committed action (writing anonymous letter), but in trying to support the conclusion of choosing one option, (A) does not address motive like the stimulus does.

Mismatched premises. (B) tries to establish that there are only two options (Carter and Whitequill) for a committed action (bribery), but this already makes (B) weak because motive is supposed to be used as a means of choosing between options. (B) may have been salvageable, but it also doesn’t tell us that our reason for eliminating one option (fearful) doesn’t apply to Carter, like the stimulus did with motive.

The argument establishes that there are only two options (Helms or Lapinski) for who committed an action (tampered with equipment). Then it eliminates one option (Lapinski) due to a lack of motive and also establishes motive in the remaining option (Helms), and then concludes that this option must be chosen (Helms).

Mismatched premises and conclusion. Like the stimulus, (D) establishes only two options (Fleming, Solano) for an action (design). But (D) doesn’t give us grounds for distinguishing between the options like the stimulus does through motive, because we don’t know about Solano’s propensity to take credit. (D) also uses an additional premise (no one took credit for the design), and there’s no counterpart for this the stimulus.

Mismatched premises and conclusion. (E) is dealing in future tense, whereas the stimulus is assigning a source to a past action, and (E) gives no reason to discount one of the options, like the stimulus did. Also, the conclusion of the stimulus is not qualified with a “probably.”