What substances move freely through the shell of the egg?

The correct answer is gases oxygen and carbon dioxide, which diffuse freely across the shell of an egg.  

The four specialized membranes of the amniotic egg are amnion, chorion, yolk sac, and allantois. The chorion and the allantois exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell.  

An eggshell refers to the outer covering of a hard-shelled egg and of some kinds of eggs with soft outer coats. The shells of the amniotic eggs are calcareous, formed of calcium carbonate.  

americans began to notice growing differences between the northern and southern sections of the country. there were more people living in cities in the north, which made it more urban. more people lived on farms in the south, which made it more rural. while many people were farmers in the northern states, there were now other ways to make a living, such as working in mechanical cotton gins factories manufacturing cloth, tools and other goods. people in the north supported high tariffs on goods imported from europe because the extra cost encouraged people to “buy american” instead. in the southern states, planters did not like tariffs because they sold most of their production to europe and bought their tools from there as well. southerners believed the protective tariff was something that only northern factory owners keep their profits high. so the southern politicians came up with an idea. they would opt out. they would simply ignore the protective tariff. it was ‘null and void’ in south carolina. the state would not collect the taxes on goods imported into south carolina, no matter what the president said they had to do. this decision led to the nullification crisis.