Question

stiff. glass reaches this state once it has cooled after introduction to intense heat. in fact, the opposite is also true. introducing a piece of glass to extreme heat can return it to a liquid form.
though this explains how glass forms, you might still be wondering how this takes place in nature. lightning is one way that glass can form in a natural setting. when a bolt of lightning hits a sandy patch of soil, it can create natural pieces of glass called fulgurites. this occurs in much the same way as we create glass synthetically. in this case, though, the bolt of lightning creates the extreme heat needed to form glass.
glass also forms naturally when lava bursts from a volcano and then cools. the melting lava creates tremendous amounts of heat. it would then make sense that a natural byproduct of the fiery volcanic explosions is a glass formation called obsidian. obsidian is a beautiful, natural spectacle. known for its shiny black, orange, gray, or green color, it was surely the earliest type of glass used by prehistoric societies. it often forms when lava spews into the sea and the water cools the lava into hard volcanic glass. unlike translucent glass, obsidian is usually opaque. this means you cannot see through this type of glass.
it was through these natural events that people discovered the amazing substance known as glass. after its discovery, people began manufacturing glass and using it for many practical and artistic purposes. today, glass is an important part of our everyday lives. just look through any window!
which best describes the organization of this passage?
a compare and contrast
b main idea and details
c sequence of events
d cause and effect

Explanation:

The passage explains how glass forms (both synthetically and naturally) by describing the causes (intense heat from lightning, volcanic lava cooling) and their effects (formation of fulgurites, obsidian, etc.). Option A is incorrect as there's no strong comparison/contrast. Option B is wrong because it's not just a main idea with details; it focuses on cause - effect. Option C is incorrect as it's not a sequence of events over time but explanations of how heat causes glass formation. So the passage is organized by cause and effect.

Answer:

D. cause and effect