According to this question, Mr. and Mrs. Green is said to have a daughter, Georgia while Mr. and Mrs. Blue is said to have a daughter, Belle. Both daughters were born the same day. Hence, a controversy occured as Mrs. Green thinks that Belle is her biological daughter.

Based on the blood analysis, the following were obtained:

Mr. Green: Type A

Mrs. Green: Type A

Georgia: Type A

Mr. Blue: Type AB

Mrs. Blue: Type A

Belle: Type O

The genotype of the following blood types is as follows:

Type A - iAiA or iAi

Type B - iBiB or iBi

Type O - ii

Type AB - iAiB

From the analysis of blood types of Mr and Mrs Green, which are both type A, they can possibly produce a child with type A.

However, from the analysis of Mr. and Mrs. Blue, it is impossible to have a child with blood type O. However it is possible for Mr and Mrs. Green if they are both heterozygous (iAi × iAi). The punnet square is attached. Hence, Mrs Green is correct about her claim since Mr. and Mrs. Blue cannot have a child with blood type A.