Although birds and mammals descended from differentancestors, they both have a four-chambered heart. Thisis the result of:
A) the necessity for rapid movement of blood.
B) convergent evolution.
C) genetic aberrations that resulted from mistakes insomatic cell division.
D) the simplification of the cardiovascular system

B) convergent evolution.

Explanation:

Convergent evolution in evolutionary biology is the process according to which, organisms that are not closely related, develop similar traits independently so that they will be able to  adapt to similar ecological niches or environments.  

Several examples of convergent evolution are shark and dolphin heads, bat and insect wings, and a four-chambered heart of birds and mammals. Analogous structures emerge from convergent evolution, but neither do homologous structures.

Hence, the correct option is B) convergent evolution.

sand 60

clay 10

silt 30

sandy loam should be dominated by the sand. as the amount of sand increased, the amount of slit needed to anchor the plants' roots to the sand will also be increased. even though the amount is very little, 10% part of clay is still necessary for proper oxidation.

answer >   yes we do, women; have three holes, urethral opening(pee hole, vagina, and the women pee/girls pee out of the urethra like the men do; only they have a single opening to pee/ejaculate.   (sorry if i'm too forward with this, but this is for a biology class, isn't it? )

hope that !         : )