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 horticulturist 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. 2 red: 2 white
B. 3 red: 1 white
C. 1 red: 3 white

To solve this problem, we need to analyze the Punnett square provided in the question. The Punnett square shows the possible genotypes from crossing two geraniums from the F1 generation. Here’s a step-by-step explanation of how to determine the expected ratio of red-to-white flowering plants:

1. Identify the Alleles:
- The allele for red flowers is represented by 'R'.
- The allele for white flowers is represented by 'r'.
- Red flowers are produced when at least one 'R' is present (i.e., genotypes RR or Rr).
- White flowers are produced only with the genotype 'rr'.

2. Analyze the Punnett Square:
The construction of the Punnett square from the question is as follows:

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

3. List the Possible Genotypes:
From the Punnett square, the possible genotypes and their frequency of occurrence are:
- RR: 1 occurrence
- Rr: 2 occurrences (there are two Rr combinations)
- rr: 1 occurrence

4. Determine the Phenotypes:
- Red-flowering genotypes are RR and Rr.
- White-flowering genotype is rr.
- From the genotypes, we have:
- 3 potential red-flowering plants (1 RR and 2 Rr)
- 1 potential white-flowering plant (1 rr)

5. Calculate the Phenotypic Ratio:
- The ratio of red-flowering to white-flowering plants is 3 red : 1 white.

Therefore, the expected ratio of red-to-white flowering plants in the F2 generation is 3 red: 1 white.