What event in March 1917 pushed the U. S. government into declaring war on Germany?

1)which is the following was characteristic of the british colonies but not the french or spanish religion a. presence of slavery b. religion conversion c. smuggling and piracy d. strict racial hierarchy 2)how did the columbia exchange affect europe? a diseases from the new world decimated the population of the european continent b new crops introduced to europe generated further interest in the new world c enslavement of american indians in europe changed cultural attitudes toward slavery d the items produced by american indians become objects of competition in europe