In the case of incomplete dominance, the traits of the offspring are a blend of the traits of the parents. If a tall plant with blue flowers (let's say blue is represented by B) is crossed with a short plant with yellow flowers (yellow could be represented by Y), the offspring would have a combination of these traits.
Since we're discussing incomplete dominance, the offspring would exhibit a mix of the flower colors. Therefore, the correct response would be:
blue and yellow flowers.
This means the flowers of the offspring would likely be a color that represents the blending of blue and yellow, not distinctly blue or yellow on their own.