Because it could be a dead give away to if someone is in danger around you.
Answer: d.
Explanation: they used them to spy on each other
Lincoln declared that they would have to accept the amendments and the new government, disband their old confederate government, make sure that former office holders could never go back into politics, and ask for an official pardon from the President of the United States. They also had to free the slaves.
The thing which was a major factor that threatened the major unity in the United States in the mid-19th century was:
<h3>The Great Depression</h3>
This refers to the period around 1929 in the United States which has a profound effect on the national economy.
This led to the failure of many banks, increase in unemployment and high deflation rates which all threatened the national unity.
Read more about Great Depression here:
brainly.com/question/441267
