试题题干
The compromise over slavery in 1850 allowed（ ）to enter the Union as a free state.
参考答案
正确答案：
试题解析
本题考查通过1850年奴隶妥协案加入联邦成为自由州的地区。
Another compromise over slavery came in 1850. California had asked to join the Union as a free state. California was admitted as a free state.
另一起奴隶妥协案发生在1850年，加州要求以自由州的身份加入联邦。之后加州被承认为自由州。
故选择A选项。