Fertilization occurs when a sperm and an egg fuse to form a diploid zygote, and male gametes are called sperm. Given these facts, fertilization occurs when an egg and what join together to form a diploid zygote among the following options:
- rapid expansion
 - testosterone
 - gastropod shells
 - penis
 - peachleaf willow
 - pollen
 - male hormone
 - male gamete


 

        male gamete 