Step 1: The cross.
In snapdragon, flower colour shows incomplete dominance. We must find the percent of pink plants in the F2.
Step 2: Meaning of incomplete dominance.
Here neither allele fully hides the other. Red ($RR$) crossed with white ($rr$) gives an in-between colour, pink.
Step 3: The F1 generation.
$RR \times rr$ gives all $Rr$, which are pink. So every F1 plant is pink.
Step 4: The F2 generation.
Now cross $Rr \times Rr$. The offspring come as $1\,RR : 2\,Rr : 1\,rr$, that is red : pink : white.
Step 5: Find the pink share.
Pink are the $Rr$ plants, which are 2 out of 4. \[ \frac{2}{4} \times 100 = 50\% \] So half the F2 plants are pink.
Step 6: Conclusion.
Therefore the correct answer is "50". \[ \boxed{50\%} \]