What caused some soldiers on the front lines to experience shell shock in world war 1?

How did the mexican war of independence differ from the american revolution? o a. only the american revolution was concerned with establishing a representative form of government. o b. only the mexican war of independence required military conflict to achieve its objectives. o c. only the american revolution succeeded in replacing a monarchy with another form of government. o d. only the mexican war of independence eliminated spanish colonial control over part of north america.