Which of the following operations on vectors u\mathbf{u}u and v\mathbf{v}v results in a scalar?
u+v\mathbf{u} + \mathbf{v}u+v
u⋅v\mathbf{u} \cdot \mathbf{v}u⋅v
u×v\mathbf{u} \times \mathbf{v}u×v
kuk\mathbf{u}ku