Test analysis: this question requires a dialectical choice, so item 1 does not meet the meaning of the question and cannot be selected; In this question, people only see the opposition between the two sides of the contradiction, but not the unity, which separates the connection between things, so this enlightens us to look at the problem from a comprehensive and connected point of view, so ② ④ Two items meet the meaning of the question and can be chosen; Item 3 does not meet the meaning of the question and cannot be selected. So, the answer is item B.