Sectional differences were increased: a. as the northeast developed into a strong industrial center b. when the invention of the cotton gin made cotton more profitable c. when pioneers moved west and demanded internal improvements d. all of the above e. none of the above

The answer is:  a. as the Northeast developed into a strong industrial center

Sectional differences refers to both cultural and economic difference that happen between american states after the civil war.  

Not long after the civil war, the northern states keep developing a strong industrialization in their territories while the southern states were left in disarray since the majority of their free labors have become a free citizen. This cause the northern states to develop faster economic growth than the southern states. and created the sectional difference.

its b i looked it up hope u get it right wish u luck

the earth’s crust is broken into separate pieces called tectonic plates (fig. 7.14). recall that the crust is the solid, rocky, outer shell of the planet. it is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. both types of crust rest atop solid, upper mantle material. the upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

each tectonic plate is free-floating and can move independently. earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. the term fault is used to describe the boundary between tectonic plates. most of the earthquakes and volcanoes around the pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. other observable results of short-term plate movement include the gradual widening of the great rift lakes in eastern africa and the rising of the himalayan mountain range. the motion of plates can be described in four general patterns:

collision: when two continental plates are shoved together

subduction: when one plate plunges beneath another (fig. 7.15)

spreading: when two plates are pushed apart (fig. 7.15)

transform faulting: when two plates slide past each other (fig. 7.15)