She knows that the trait of red flowers is governed by the allele [tex]R[/tex] ([tex]RR[/tex] and [tex]Rr[/tex]), and the trait of white flowers is governed by the allele [tex]r[/tex] ([tex]rr[/tex]).

The horticulturalist crosses two geraniums from the F1 generation. Look at the Punnett square to see this cross.

[tex]
\[
\begin{array}{|c|c|c|}
\hline
& r & r \\
\hline
R & Rr & Rr \\
\hline
r & rr & rr \\
\hline
\end{array}
\]
[/tex]

Which ratio of red-to-white flowering plants would she expect to see in the phenotypes of the F2 generation?

A. 3 red to 1 white
B. 1 red to 3 white
C. All red
D. 2 red to 2 white

To determine the ratio of red-to-white flowering plants in the F2 generation, we need to analyze the provided Punnett square, which represents the genetic cross of two geraniums from the F1 generation.

Here's the Punnett square:

[tex]\[
\begin{array}{|c|c|c|}
\hline
& r & r \\
\hline
R & Rr & Rr \\
\hline
r & rr & rr \\
\hline
\end{array}
\][/tex]

Steps to determine the phenotypic ratio:

1. Identify the Genotypes:
- There are four possible offspring:
- Two cells with the genotype Rr (from the combinations: R and r).
- Two cells with the genotype rr (from the combination: r and r).

2. Determine the Phenotypes:
- Rr: This genotype represents red flowers because the presence of the dominant allele [tex]\( R \)[/tex] is enough to express the red flower trait.
- rr: This genotype represents white flowers because both alleles are recessive [tex]\( r \)[/tex].

3. Count the Phenotypic Outcomes:
- There are 2 occurrences of Rr (red flowers).
- There are 2 occurrences of rr (white flowers).

4. Calculate the Phenotypic Ratio:
- The phenotypic ratio of red flowers (Rr) to white flowers (rr) is 2:2.

5. Simplify the Ratio:
- Simplify the ratio 2:2 to its simplest form, which is 1:1.

Based on this analysis, the horticulturalist should expect to see a 1 red to 1 white ratio in the phenotypes of the F2 generation. Therefore, the correct choice is 2 red to 2 white or simply 1 red to 1 white.