Final answer:
Star B, the nearby star, will have the largest blueshift.
Step-by-step explanation:
In this scenario, the star that will have the largest blueshift is Star B, the nearby star.
Blueshift occurs when an object is moving towards the observer, causing the wavelengths of light to appear shorter, shifting towards the blue end of the spectrum.
Since Star A is really far away, its motion across our line of sight will have a minimal effect on the observed blueshift. On the other hand, Star B, being nearby, will have a greater impact on the observed blueshift.