Answer:
Option B, incomplete dominance
Step-by-step explanation:
In incomplete dominance, the two alleles that pair up to express a trait restricts the sole expression of characteristics associated with individual allele. Thus the offspring’s produced have completely different characteristics/trait as compared to the paired parent's allele’s characteristics/trait.
Here in this case neither the blue nor the yellow color of the flower expresses themselves completely thereby producing entirely different color flowers i.e green flowers.
A very common example of incomplete dominance is production of pink flowers when white and red flowers are crossed.