If cv=0c\mathbf{v} = \mathbf{0}cv=0, which of the following must be true?
c=0c = 0c=0
v=0\mathbf{v} = \mathbf{0}v=0
c=0c = 0c=0 or v=0\mathbf{v} = \mathbf{0}v=0
ccc is any number.