The points with position vectors $\overline{\mathrm{a}}+\overline{\mathrm{b}},\overline{\mathrm{a}}-\overline{\mathrm{b}}$ and $\overline{\mathrm{a}}+\mathrm{k}\overline{\mathrm{b}}$ are collinear

for exactly two values of k

for exactly three values of k

for all real values of k

for no real value of k