Answer:
The most likely answer is B.
Step-by-step explanation:
A. is incorrect because the Missouri Compromise admitted Missouri as a slave state and Maine as a free state.
B. could be a possible answer, because in 1850, as a part of the Compromise of 1850 the northern boundary of the Texas Panhandle was fixed at the Missouri Compromise line, thus avoiding conflict in interpretations and making Texas a "slave state."
C. This is true however, the Missouri Compromise was declared unconstitutional by the Supreme Court in the Dred Scott decision, which ruled that Congress did not have the authority to prohibit slavery in the territories.
D. Slavery was not allowed to spread to all states, except Missouri, this law prohibited slavery in the Louisiana Territory north of the 36° 30´ latitude line.