Answer:
Incomplete dominance
Step-by-step explanation:
When you cross two true breeding parents, a red and a white snapdragon you would normally expect at least some of the offspring to have these same traits. The fact that all of the F1 have a completely different phenotype (pink flowers) indicates the existence of incomplete dominance, in which one of the phenotypes (red) is only partially dominant over the other (white). When you cross the F1 with each other then you again see the original phenotypes, red and white reappear.