Magnetic force: $\vec{F} = q\vec{v}\times\vec{B}$. For particle 1 ($q_1=-q$, $\vec{v_1}=v_1\hat{i}$): $\vec{v}\times\vec{B} = v_1\hat{i}\times B_0\hat{k} = v_1B_0(\hat{i}\times\hat{k}) = -v_1B_0\hat{j}$. With $q_1=-q$: $\vec{F_1} = (-q)(-v_1B_0\hat{j}) = +qv_1B_0\hat{j}$ (force along $+y$). For particle 2 ($q_2=+2q$, $\vec{v_2}=v_2\hat{i}$): $\vec{F_2} = (2q)(-v_2B_0\hat{j}) = -2qv_2B_0\hat{j}$ (force along $-y$). Since the initial forces are in opposite directions, the two particles curve in opposite senses. Working out the rotation sense: particle 1 turns anticlockwise while particle 2 turns clockwise. Hence the correct option is (D).