Mathematics

Problem

Match the items of Column I with items of Column II.

Column I	Column II
A. If $\mathbf{a} + \mathbf{b} = \mathbf{a} + 2\mathbf{b}$ , then angle between $\mathbf{a}$ and $\mathbf{b}$ is	p. $90^\circ$
B. If $\mathbf{a} + \mathbf{b} = \mathbf{a} - 2\mathbf{b}$ , then angle between $\mathbf{a}$ and $\mathbf{b}$ is	q. obtuse
C. If $\mathbf{a} + \mathbf{b} = \mathbf{a} - \mathbf{b}$ then angle between $\mathbf{a}$ and $\mathbf{b}$ is	r. $0^\circ$
D. Angle between $\mathbf{a} \times \mathbf{b}$ and a vector perpendicular to the vector $\mathbf{c} \times (\mathbf{a} \times \mathbf{b})$ is	s. acute