Considering that portals are quite literally linked in a spatial manner, it would make sense that they physically cannot move independantly. Moving the orange portal would also move the blue portal. Or from a different perspective: the portals are always fixed in space, but their surrounds can move.

But that does not make the question shown here untestable. It just means the output portal will have a velocity of it's own.

How to test: place 2 portals next to each other on a wall. Then apply propulsion gel in front of the orange portal. And finally move yourself at high speed through the orange portal.

If your speed is unchanged after exiting the blue portal, but your velocity has been inverted with respect to the direction that the wall is facing, we can conclude option B must hold.