Historians use primary sources like diaries, letters, speeches. And secondary sources like articles.
Answer:
Two-field system
Explanation:
Two-field this is more than 1 and there are more crops being grown
Causes<span> include controversy over admitting Missouri as a slave state in 1820, the acquisition of Texas as a slave state in 1845 and the status of slavery in western territories won as a result of the Mexican–American </span>War<span> and the resulting Compromise of 1850.
Hope this Helped :)</span>
The U.S politicians and businessmen worried about the foreign nations controlled economic development so they supported open door policy
Grace period seems correct
