A) threatening the life of a leader
To write to a government representative is encouraged if the matter is of importance. This is done by those who are trying to argue a point, for example people protesting a new law or company. This is perfectly legal.
The right to peaceful assembly or protests is protected under the First Amendment. This is legal.
Signing a petition is also perfectly legal, as no physical harm is involved to another person.
I hope this helps! :)
