In a cross, when genotypic ratio and phenotypic ratio in $F_2$ generation are same, the alleles show:

Incomplete dominance

The correct answer is Option (3) → Incomplete dominance

The inheritance of flower colour in the dog flower (snapdragon or Antirrhinum sp.) is a good example to understand incomplete dominance. In a cross between true-breeding red-flowered (RR) and true- breeding white-flowered plants (rr), the F1 (Rr) was pink. When the F1 was self-pollinated the F2 resulted in the following ratio 1 (RR) Red : 2 (Rr) Pink : 1 (rr) White.

Here the genotype ratios were exactly as we would expect in any mendelian monohybrid cross, but the phenotype ratios had changed from the 3:1 dominant : recessive ratio. What happened was that R was not completely dominant over r and this made it possible to  distinguish Rr as pink from RR (red) and rr (white).

 Results of monohybrid cross in the plant Snapdragon, where one allele is incompletely dominant over the other allele.

• Complete dominance is when the dominant allele completely masks the effect of the recessive allele in the heterozygous condition. For example, in Mendel's pea plants, the allele for tall plants (T) is completely dominant over the allele for short plants (t), so both TT and Tt plants are tall.
• Co-dominance occurs when both alleles in a heterozygous individual contribute to the phenotype. In the case of the ABO blood group system, the I^A and I^B alleles are co-dominant. This means that if an individual has both I^A and I^B alleles (genotype I^AI^B), both alleles are expressed, and the individual has blood type AB, which has both A and B antigens on the surface of the red blood cells.
• Polygenic inheritance occurs when one character is controlled by two or more genes. Often the genes are large in quantity but small in effect. Examples of human polygenic inheritance are  skin colour, eye colour.