Why do men get 'morning wood', and what causes it?

Me with biology endocrine system crossword also image left i need with hw

Which is the correct formula for photosynthesis

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.