What event marked the beginning of world war ii in europe

Germany invasion in Poland in September 1939.

Explanation:

when Hitler was setting his sights on Poland in his plight to expand his empire, this was the last straw. As soon as Hitler attacked Poland, Britain and France declared war against Germany. thus starting world war II

answer; the mayans and

crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.