What she means is that she had made 19 trips to Maryland, helped 300 people to freedom, yet she was never captured and didn’t fail to deliver her "passengers" to safety. As Tubman herself said, "On my Underground Railroad I [never] run my train off [the] track [and] I never [lost] a passenger." During these journeys she helped rescue people that were from her own family and people who weren’t from her own family. You can check her story in the America Library.
C. Juliet expresses her fear that the promises made between her and Romeo will not last.
Answer: but
Explanation:
In 1863, President Abraham Lincoln designated the last Thursday in November as a national holiday of Thanksgiving ....... in 1939, President Franklin Roosevelt decreed that the holiday should always be celebrated on the fourth Thursday of the month.
Out of the options given, the answer is "but". This is the right answer as it'll be used to link both sentences regarding the two activities of the President's together.
The other options such as "for example", "therefore" and "so" when used doesn't make the sentence correct.