Hostile acts of expansionism by the three countries during the 1930s sowed the seeds of world war. Fascist Italy invaded Ethiopia on October 3, 1935. Imperial Japan, which had occupied Manchuria (Northeast China) since 1931, engaged Chinese troops near Beijing on July 7, 1937, thus launching full-scale warfare there
Answer:
C. Primary or Secondary sources related to the event.
Explanation:
A historian using primary or secondary resources related to the events is the most reliable.