Answer:
The correct answer would be 3 blue 1 white.
It can be explained with the help of monohybrid cross.
Let us assume the alleles of the gene responsible for flower color in pea plant be:
B: Dominant allele results in the formation of blue color.
b: recessive allele results in the formation of white color when present in homozygous condition.
Now, both the parents crossed were heterozygous and thus the genotype of both would be Bb.
The gametes produced would be B and b.
The cross, in the form of Punnett square is shown in the figure attached.
The genotypic ratio observed was 1 : 2 : 1 = BB : Bb : bb.
The phenotypic ratio observed was 3 : 1 = blue : white.
