Analysis of test questions: This question aims to examine students' understanding of the causal relationship of historical events. According to the knowledge learned, ① the policy of establishing a national anti-Japanese national United front was put forward at the meeting of the CPC Wayaobao in February 1935, and ② the Xi incident occurred under the inspiration of the rising ethnic contradictions and the anti-Japanese national United front of the CPC. 1936 12 February 12 The peaceful settlement of the Xi Incident initiated by Zhang Xueliang and Yang Hucheng marked the basic end of the ten-year civil war between the Kuomintang and the Communist Party and the initial formation of the anti-Japanese national united front. After the September 18th Incident, Japan launched a war of aggression against China, and ethnic contradictions began to rise, so ④ started at the earliest, and the order of causality was ④ ① ② ③.

Comments: This question is less difficult. To examine students' memory ability of historical knowledge, generally, the occurrence of a historical event always has its background (cause), process, result and influence. When we explore historical events, we should first explore the background reasons why it happened, know why it happened and know the true face of history.