Which weapon was a primary cause of the u. s. entry into world war i?

The United States entered the war because of the Germans' decision to resume the policy of unrestricted submarine warfare.  

it is the code of hammurabi

in 1803 the louisiana purchase took place, doubling the size of the country. by 1840 almost 7 million americans had migrated westward in hopes of securing land and being prosperous. the belief that settlers were destined to expand to the west is often referred to as manifest destiny.

explanation: