Answer: Imperialism
Explanation: European expansion into the western world was the biggest factor in them becoming involved into world war I.
The best and most correct answers among the choices provided by the question are the following
<span> 1. The slave trade was ended in the North. Missouri was admitted as a slave state.
2. Popular sovereignty was established for New Mexico and Utah.
3. California was admitted as a free state.
4. A stringent fugitive slave law was passed Slaves would be freed if they went into the Northeastern states.
5. The slave trade was outlawed in the District of Columbia.</span>
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I think the answer to this is A
