20. When people predict that certain result will not take place unless a certain action is taken, they believe that they have learned that the prediction is correct when the action is taken and the result occurs. On reflection, however, it often becomes clear that the result admits of more than one interpretation.

Which of the following, if true, best supports the claims above?

(A) Judging the success of an action requires specifying the goal of the action.

(B) Judging which action to take after a prediction is made requires knowing about other actions that have been successful in similar past situations.

(C) Learning whether a certain predictive strategy is good requires knowing the result using that strategy through several trials.

(D) Distinguishing a correct prediction and effective action from an incorrect prediction and ineffective action is often impossible.（D）

(E) Making a successful prediction requires knowing the facts about the context of that prediction.

这题就没看懂意思，哪位NN能给讲一讲吗？先谢了！

"Somebody predicts that a certain action is necessary for a certain result. If when the action is taken, the result indeed occus, then this person will think that his prediction is proven. However, the author says, the result might have been caused by some other factors -- not necessarily the action."

Paraphrase of D: It's impossible to tell a correct prediction (and effective action) from an incorrect prediction (and ineffective action).