MAGOOSH Official Explanation:
(A) This question is an example of how the GMAT will sometimes choose an OA that is less than ideal. (A) is an example of such an imperfect sentence. Typically, a comma doesn’t follow “that”. Here it is okay because we are reversing the clause, “we need to converse with a native speaker to speak a foreign language”, becomes “to speak a foreign language, we need to converse with a native speaker”.
(B) The phrase beginning with “with” should logically modify the subject “the paradigm," but in this case it does not logically do so. The paradigm is actually that we need to converse with a native speaker. Thus, this is an example of a misplaced modifier.
(C) A clause beginning with “with” is always suspect on the GMAT, since it usually illogically modifies what comes after the comma. This case is no different. Does the action of foreign-language moving online describe the act of “conversing with a native speaker”? The two are clearly independent. Also, the “which” does not have a clear referent.
(D) implies that the paradigm has become swiftly obsolete. It also says that "the need to converse with a native speaker to speak a foreign language" is the paradigm because foreign language learning moves online. This is illogical and changes the meaning.
(E) After a long beginning adverbial clause, separating the subject “paradigm” from the verb with a long relative clause is a no-no. The more obvious error, however, is the “paradigm, which”. We are describing a specific paradigm, not all paradigms in general. Therefore, we want “that”. Finally, there is a slight change in meaning. The original sentence says the paradigm is becoming obsolete. (E) implies the paradigm has already become obsolete.
Answer: (A)