Am what animal sperm cells move on so that they can reach an egg surface hairs rigid walls muscle flagella

The correct answer is: flagella.

Animal sperm cells are motile meaning that they move via flagella and require a water medium in order to swim toward the egg for fertilization. This process requires energy which can be derived from sugar metabolism. Usually, sperm cells are uniflagellated (with one flagellum) and called spermatozoa.

i believe the answer is a or 1

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.