After fertilization, which type of cellular division is responsible for the growth and development of a complex, multicellular organism?

Fertilization between the haploid gametes forms a diploid zygote. The zygote will undergo many rounds of mitosis and give rise to a diploid multicellular plant called a sporophyte. ... The spores will then develop into the multicellular gametophytes.

https://www.khanacademy.org/science/biology/cellular-molecular.../sexual-life-cycles

Khan academy is a great learning tool for subjects you don't understand of if you need to go back and learn something

l think it is 3 three^_^^_^^_^^_^^_^^_^^_^^_^^_^