This text is organized into two main parts. The first part describes Naveena Shine's experiment and its results. What does the second part mostly describe?

How do the sperm cells get from the stigma to the ovules? a. they slide down the petals to the bottom of the flower. b. they travel through pollen tubes. c. they travel along filaments. d. insects carry the sperm cells from the stigma to the ovules.