Why do Mercury and Venus not have moons? Select one:
O a. The sun's gravity would have pulled any orbiting moons into the sun.
O b. These planets are moving too fast to support any orbiting satellites.
c. Mercury and Venus do have moons!
d. There was not an impact or asteroid capture on these planets because the asteroid belt is too far away.
e. These planets are not large enough to have orbiting satellites

Ablastocyst is a group of cells that forms after a human egg is fertilized. the blastocyst consists of two types of cells. some of these cells will become the placenta. what do the other cells develop into?

Control of the body is accomplished by which of the following body systems? nervous system and circulatory system endocrine and repertory system circulatory and respiratory systems nervous system and endocrine systems

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.