Step 1: Understanding the Concept
This is a "Flaw in Reasoning" question, specifically one that involves applying a principle. The flaw usually lies in a misinterpretation or misapplication of the terms in the principle.
Step 2: Detailed Explanation
Let's break down the components:
Principle: Not Prudent \(\leftarrow\) Unacceptable Risk. (If risk is unacceptable, strategy is not prudent).
Evidence about Noah: Strategy includes less stable assets.
Conclusion about Noah: Strategy is not prudent.
The Gap: The argument moves from "exposure to less stable assets" directly to the conclusion "not prudent." To do this using the principle, it must implicitly equate "exposure to less stable assets" with "an unacceptable level of financial risk." This is a significant logical leap. A small exposure to less stable assets might increase risk slightly but not necessarily to an "unacceptable" level. The argument fails to justify that this threshold has been crossed.
Step 3: Final Answer
Let's analyze the options:
(A) This is a valid point about diversification, but the core flaw is in the assumption about risk level, not the mechanics of diversification.
(B) This perfectly captures the flaw. The argument assumes that *any* increase in exposure to volatile assets automatically means the overall risk level is now "unacceptable." It takes a necessary condition from the evidence ("less stable") and treats it as sufficient to trigger the condition in the principle ("unacceptable").
(C) The argument doesn't assume this is *always* true, just that it is in this case.
(D) The principle is about risk, not returns. High potential returns do not negate the risk, so this is not a flaw in applying the principle.
Option (B) points out the unjustified leap in logic: the argument assumes without evidence that the risk has crossed the "unacceptable" threshold.