Some members of a photosynthetic plant species are genetically resistant to an herbicide, while other members of the same speciesare resistant to the herbicide. Maintaining resistance against theherbicide is metabolically metabolically expensive for the plants. Which combination of events should cause the most effective replacement of the non-herbicide-resistant strain of plants by theresistant strain?

1. an abundance of sunny weather
2. an abundance of cloudy weather
3. the presence of the herbicide in the environment
4. the absence of the herbicide from the environment
5. the maintenance of the proper conditions for one generation
6. the maintenance of the proper conditions for manygenerations

a.2, 4, and 5
b.2, 3, and 5
c.1, 4, and 6
d.1, 3, and 6
e.2, 3, and 6