What process marks the birth of a star? a. a supernova explosion
b. when it begins combining hydrogen to form helium
c. when its mass expands and cools
d. when gravity pulls in nebular dust

1. describe the structure and function of the specialized cells you observed in the video. 2. research the types of cells present in the kidney.

The table lists the observations students made about four specimens under a microscope. based on these observations, what specimens did the students examine? animal plant virus prokaryote cell membrane present ribosomes present lysosomes present nuclear membrane present cell wall present ribosomes present nuclear membrane absent cell wall present ribosomes present nucleus present large vacuole present reproduces inside of a cell nucleus absent rna present 2019 edmentum all rights reserved intl

Which line in the graph above best illustrates an effect of the carbon dioxide level in the blood on breathing rate before, during and after a period of exercise? 1.b,2.c,3.a,4.d