Like all flowering plants, the snapdragon must be pollinated to reproduce, but its flowers are closed. A bumblebee has just enough weight to open a snapdragon flower by landing on it. This adaptation is an example of:

Explanation:

Coevolution : It is the influence of closely associated species on each other in their evolution, they affect each other.

In coevolution , two or more species reciprocally affect  evolution of  each other by natural selection.

Coevolution Examples:

There are lots of examples of coevolution, some are here

i) coevolution of Predator-Prey , this relationship is one of the most common examples of coevolution.

ii) coevolution of  Herbivores and plants,

iii)  coevolution of Acacia ants and Acacias and

iii)  coevolution of Flowering Plants and Pollinators and many others.

the answer to your question is b