What was one reason why the spanish civil war was called a “dress rehearsal” for world war ii?

Their motto was to keep madrid the tomb of facism. they also fought with other countries. The spanish civil war is known the dress rehearsal for world war two because it was in time in which new weapons and technologies could be tested for use. The sspanish civil war ended in 1939 the same year the world war two  started.

The answer is option b and c.