Emma and anna are identical twins who were adopted by different families a few weeks after their birth. although genetically identical, they grew up with different physical and psychological characteristics. for example, though both inherited a tendency to grow large, anna was slim and athletic because of the active lifestyle practiced in her adoptive family. this variability can be explained by how:
a. each zygote is unique. b. longevity genes can make an individual less vulnerable to certain diseases. c. for each genotype, a range of phenotypes can be expressed. d. mutated genes can be a source of genetic variability.

The persians landed in the plains near athens. as their army greatly outnumbered that of the greeks, the greeks hoped to find aid from nearby sparta. a long-distance runner named pheidippides was sent from athens to sparta to request , but the spartans were not able to send more soldiers at the time. regardless, the greeks were still able to win the battle. centuries later, legend developed that a runner had been sent from the battle to athens after the greek victory. after reaching athens, the runner proclaimed, "we are victorious! " and then fell to the ground and died. this legendary story is the inspiration for the modern long-distance runs that are performed today. this passage refers to the events of which battle during the persian wars? a. battle of thermopylae b. battle of salamis c. battle of plataea d. battle of marathon

Which of the following items would serve as a primary source for a historian studiying the american civil war

What was one step that charlemagne took to unite his kingdom? a. he chose a single strong heir to inherit his throne. b. he drove muslim forces out of europe. c. he created and supported schools. d. he declared himself head of the catholic church.