The layer is above stratosphere and below thermosphere, this is where meteors and rock fragments burn up and is the coldest layer of the atmosphere. This is
A) troposphere
B) stratosphere
C) mesosphere
D) thermosphere

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.