How does the deletion of a single base cause a frameshift mutation?

What causes darkening of the skin as melanin production increases

The vaccine in a flu shot contains weakened flu viruses. how does a flu shot work with the immune system? a. it destroys lymphocytes. b. it destroys macrophages. c. it activates macrophages. d. it activates lymphocytes.

Kudzu vines grow by climbing and wrapping around trees. trees covered by kudzu can die because they are starved of sunlight. what type of relationship exists between the trees and the kudzu growing on them?