Correct answer: (C) Translate along +y at speed $\Gamma/(2\pi h)$.
Explanation
At distance h, one point vortex induces speed $\Gamma/(2\pi h)$. The drawn opposite circulation senses make the induced velocity at each vortex point upward. Since both have equal induced translational velocities, their separation stays h and the pair translates in +y, rather than rotating about the midpoint. Select C.
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