Serene City Enacts an Ordinance That Bans the Use of "Sound

Serene City enacts an ordinance that bans the use of "sound amplifying systems" on public streets. Tom wants to campaign for a seat on the city council by broadcasting his message through speakers mounted on a truck. In Tom's suit against the city, a court would likely hold this ordinance to be

A) constitutional under the First Amendment.
B) not subject to the U.S. Constitution.
C) unconstitutional under the commerce clause.
D) unconstitutional under the First Amendment.