You are presented with the question "What causes fertilization?" and the following answer choices: 
- pollen
 - infertility
 - gametes
 - orchids
 - seeds
 - no physical contact
 - honeybees
 - isolation

Now knowing that fertilization occurs when a sperm and an egg fuse and sperm and eggs are cells known as gametes, choose the best answer.


 

   gametes      