Answer:
If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency.
Step-by-step explanation:
The new virus will be resistant to Tamiflu. The Tamiflu resistance gene will become common in the environment due to directional selection. Directional selection can be described as a condition in which one phenotype is favoured such that the phenotype becomes abundant in an area and hence the allele frequency of the area changes. This occurs because that phenotype is better adapted to survive in an environment.