There's many answers for this question, as long as it's a similar word to disbelief. President Roosevelt's reaction was pretty much thinking, "This is unbelievable." So therefore, you can put disbelief or distrust.
The correct answer is (c)
It helped power the trains and steam boats.
I'm not sure if you made a typo or not but in the current context I can only see negligible being relevant.
Answer:
The Constitution thus protected slavery by increasing political representation for slave owners and slave states; by limiting, stringently though temporarily, congressional power to regulate the international slave trade; and by protecting the rights of slave owners to recapture their escaped slaves.
Explanation: