2. Which of the following best explains why the cell membrane is described as selectively permeable? * A. 
Substances are not allowed into the cell.
* B. 
Substances diffuse freely in and out of the cell.
* C. 
Some substances pass into the cell while others cannot.
* D. 
Some substances can move into the cell but not out of the cell.

Consider darwin's first writings on the theory of natural selection. an important point of darwin's essay on the principle of population, written in 1798, was a peer's observation that in nature plants and animals produce far more offspring than can survive, this observation can be attributed to a) charles lyell. b) thomas malthus. c) jean-baptiste lamarck. d) johann friedrich meckel.

What molecules does hemoglobin decay into over time

If t=tall and t=short what will be the physical appearance of the offspring the cross below? a.some will be tall and some will be short b.they will all be tall c.they will all be short d.they will be medium height