Introduction:
This question pertains to the inheritance pattern of flower color in plants, which is controlled by a single gene with two alleles- red and white. When two different homozygous plants with different alleles for flower color are crossed, the resulting F1 generation shows only one of the two colors. However, in F2 generation, both colors reappear in a specific ratio. This ratio depends on the genotypes of the parent plants and follows the laws of probability and segregation.

Explanation:
Given, the ratio of red and white flowers in F2 generation is 60:20, which simplifies to 3:1. This means that out of 4 total offspring, 3 have red flowers and 1 has white flowers. This can only happen if the parent plants in the cross were heterozygous for flower color, i.e., Rr and Rr. Here, R represents the dominant allele for red color and r represents the recessive allele for white color.

When two heterozygous plants are crossed, the gametes they produce can combine in four possible ways- RR, Rr, rR, and rr. The probability of each combination is 1/4 or 25%. The resulting phenotypic ratio in F2 generation is 1:2:1 for RR:Rr:rR:rr. Here, RR and rr are purebred or homozygous for red and white colors respectively, and Rr and rR are both heterozygous for red color.

Since the ratio of red and white flowers in F2 is 3:1, it means that 3 out of 4 offspring are heterozygous for red color and 1 out of 4 is homozygous for white color. Therefore, the genotype of F2 plants can be represented as Rr:Rr:Rr:rr. When the heterozygous red-flowered plants (Rr) self-pollinate, the resulting offspring will also follow a specific ratio, which is called the Mendelian ratio or the Punnett square ratio.

The Punnett square for selfing Rr plants is:

| | R | r |
|---|---|---|
| R | RR| Rr|
| r | Rr| rr|

The resulting phenotypic ratio is 1:2:1 for RR:Rr:rr, which means that out of 4 total offspring, 1 has red flowers and is homozygous (RR), 2 have red flowers and are heterozygous (Rr), and 1 has white flowers and is homozygous (rr). This ratio simplifies to 1:2:1 or 25%:50%:25%.

Conclusion:
Therefore, the correct option is A)72:24, which is equivalent to 3:1 when simplified. This ratio represents the F2 generation of a cross between heterozygous red and white flowered plants. When the heterozygous red-flowered plants are selfed, the resulting offspring follow a Mendelian ratio of 1:2:1 for RR:Rr:rr, which simplifies to 25%:50%:25%.