The scalar triple product $\mathbf{a}\cdot(\mathbf{b}\times\mathbf{c})$ is a scalar — it gives the volume of the parallelepiped formed by the three vectors. Option (A) $(\mathbf{a}\cdot\mathbf{b})\mathbf{c}$ is a vector (scalar times vector); option (C) is a vector triple product (vector); option (D) is zero vector.