"Braille prints letters as raised dots a reader feels with the fingertips. Each character sits in a cell of up to six dots, so touch alone tells one letter from another." What is the central idea?

"A tree adds one growth ring a year, wide in a wet year and narrow in a dry one. Because whole forests share the pattern, researchers can date an old beam by matching its rings to dated wood." Which statement best expresses the central idea?

"Hatchling sea turtles crawl toward the brightest horizon, which on a dark beach is the open ocean. Beachfront lights can pull them inland instead, so coastal towns now shield lamps to aim the light downward." What is the central idea?

"A Roman aqueduct moved water without a pump. Surveyors cut its channel so that it dropped only slightly along its whole length, and arches carried the channel across valleys at that same gentle slope." What idea does the whole passage support?

"A sourdough starter is a paste of flour and water that wild yeasts and bacteria live in. The yeasts give off gas that lifts the dough; the bacteria give off acids that sour it. A baker feeds the starter to keep both alive." What is the central idea?

Frederick Douglass wrote: "I soon learned the names of these letters ... my copy-book was the board fence, brick wall, and pavement; my pen and ink was a lump of chalk. With these, I learned mainly how to write." What is the central idea?

In a passage explaining that a public library now lends far more than books, which of these is a supporting detail rather than the central idea?

A paragraph explains that the human body keeps time by light rather than by the clock on the wall. Which sentence works as a supporting detail?

A short article makes the point that the potato helped feed a growing northern Europe. Which of these is a detail that supports the point rather than the point itself?

In a passage about why hospitals ask every visitor to wash their hands, which statement is a supporting detail rather than the central idea?

A passage argues that fire lookouts once watched whole forests from towers. Which sentence below is a supporting detail?

At Gettysburg, Lincoln said: "We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this." Best objective summary?

"Salt spread on a road dissolves in the film of water on the ice and lowers the temperature at which that water can refreeze. When the road is very cold, too little melts for salt to work, so crews spread sand for grip." Best objective summary?

"A lighthouse lamp on its own scatters light in every direction. Rings of shaped glass set around it bend the stray light forward into one narrow beam. The same lamp can then be seen from far out at sea." Which summary is both complete and neutral?

"Many vaccines lose strength if they warm up. Clinics far from a power supply carry doses in insulated boxes packed with ice. A card of heat-sensitive dots on the box shows whether a shipment ever got too warm." Which is the best objective summary?

"A beaver dams a stream to raise a pond deep enough that the entrance to its lodge stays under water. The pond that results slows the current, traps silt, and floods ground that other animals then use." Which is the best objective summary?

A paragraph explains that carrier pigeons could deliver messages because a released bird flies home from unfamiliar country. Which sentence does NOT develop that idea?

A short article argues that streetlights changed how a city used the night. Which detail does NOT support that claim?

A passage explains that the printing press spread ideas faster than copying by hand ever could. Which sentence fails to develop that central idea?

A paragraph explains that a coral reef depends on algae living inside the coral animal. Which detail does NOT belong?