Single choice · #803
The IT department's operations policy clearly states: “If an incorrect password is entered three times, the account will be locked.” During the morning inspection, Xiao Li saw that Xiao Zhang's account was locked. Xiao Li then reported to the supervisor: “So Xiao Zhang must have entered the wrong password three times.” What is the flaw in Xiao Li's reasoning?
Show answer & explanation
Answer: A
- AThe account might have been locked because an administrator manually deactivated it, so it cannot be concluded that wrong passwords caused the lock.✓ Correct: it points out that there are other ways an account can be locked, so one cannot work backward and infer that wrong passwords must have occurred.
- BThe inference is entirely valid, because the operations policy clearly states that wrong passwords lead to an account being locked.✗ Wrong: this misunderstands the rule by assuming that as long as the rule itself is true, the cause can be worked backward from the result — this is exactly the fallacy of affirming the consequent.
- CThe flaw is that Xiao Li is using “no wrong password was entered” to infer “the account definitely will not be locked.”✗ Wrong: this misattributes the error, describing the mistake of reasoning backward from result to cause as if it were reasoning from a cause not occurring to a result not occurring.
- DThe flaw is that Xiao Li did not pull the login logs, so the exact moment the account was locked cannot be precisely confirmed.✗ Wrong: this attacks an operational detail irrelevant to the logic of the inference and does not point out the flaw in the reasoning itself.
Explanation:According to the rule, entering a wrong password three times will indeed cause the account to be locked, but this does not mean locking is the only possible outcome of that action — nor that locking could only come from that action. The account may have been locked for other reasons, such as a security freeze triggered by long inactivity, or an administrator manually deactivating it from the back end. Xiao Li saw only that the account was locked and concluded it must have been caused by wrong passwords, ignoring other possible causes of the lock, so the conclusion does not hold. This is the classic fallacy of affirming the consequent: from “if P then Q” and “Q is true,” one cannot validly infer “P is true.”