(1) Bees fan their wings at the hive door on hot days. (2) A hive holds tens of thousands of bees. (3) Workers carry in water and spread it on the comb. (4) Bees also gather pollen for the larvae. Which pair supports the inference that bees cool the hive?

(1) Sea otters eat large numbers of sea urchins. (2) Sea urchins graze on the roots of kelp. (3) Otters have the densest fur of any mammal. (4) Kelp forests shelter many young fish. Which pair supports the inference that otters protect kelp?

(1) Emperor penguins breed on sea ice. (2) Birds on the outside slowly shuffle to the middle. (3) Emperors are the largest of all penguins. (4) The middle of a huddle stays far warmer than the edge. Which pair shows that each bird gets a warm turn?

(1) Camels can drink many gallons of water at once. (2) Two rows of long lashes keep sand from their eyes. (3) A camel's hump stores fat, not water. (4) That fat can be broken down for energy. Which pair shows the hump helps a camel go without food?

(1) Rome also built long paved roads. (2) Aqueduct channels sloped gently downhill for miles. (3) Water ran through them without any pump. (4) Some aqueducts crossed valleys on stone arches. Which pair shows aqueducts moved water by gravity?

(1) A tree adds one new ring of wood each year. (2) Foresters can count the rings on a cut stump. (3) Oak wood is heavy, hard, and slow to rot. (4) Rings formed in wet years are wider. Which pair shows a ring's width records one year of weather?

(1) Monarchs fly to the same fir forests in Mexico each fall. (2) Adults sip nectar from many flowers. (3) No single butterfly lives long enough to make the round trip. (4) Caterpillars feed only on milkweed. Which pair shows no parent teaches the route?

(1) Antarctica is the coldest place on Earth. (2) Deep ice holds bubbles of air trapped long ago. (3) Drilling a core takes weeks. (4) Scientists measure the gases inside those bubbles. Which pair supports the inference that ice cores reveal ancient air?

(1) Earthquakes send energy through the ground as waves. (2) Sensors are buried across the state. (3) Fast P waves arrive before the damaging S waves. (4) Sensors alert the city the instant a P wave hits. Which pair shows a warning can beat the shaking?

(1) An owl's wing feathers have soft, fringed edges. (2) Those edges muffle the sound of each wingbeat. (3) Owls swallow small prey whole. (4) An owl's eyes face forward. Which pair supports the inference that an owl can reach prey unheard?

(1) A trap shuts only after two hairs are touched in quick order. (2) The plant grows in poor, sandy soil. (3) Its flowers rise on a tall stalk. (4) Closing on nothing costs energy the plant cannot spare. Which pair shows the two-touch rule saves energy?

(1) The Erie Canal opened in 1825. (2) It linked the Hudson River to Lake Erie. (3) Freight rates between Buffalo and New York City fell sharply. (4) Mules walked a towpath beside the water. Which pair shows the canal cut the cost of western goods?

(1) Bristlecone pines grow very slowly on dry, windy peaks. (2) Their cones carry short bristles. (3) Slow growth builds wood so dense that rot spreads poorly. (4) The pines grow above 9,000 feet. Which pair shows a harsh site helps these trees live long?

(1) Many bats roost in caves by day. (2) A hunting bat sends out clicks and listens for echoes. (3) Some bats have wingspans of five feet. (4) The echoes tell it where a moth is flying. Which pair supports the inference that bats can hunt in the dark?

(1) Beavers cut saplings with strong front teeth. (2) A lodge is entered from under the water. (3) A beaver dam slows a stream into a wide pond. (4) Frogs, ducks, and fish move into the new pond. Which pair shows beavers make homes for other animals?

(1) Recycling a can uses about five percent of the energy of making a new one. (2) A recycled can may be back on a shelf in two months. (3) Aluminum comes from bauxite ore. (4) Cans are sorted by machine. Which pair shows recycling saves energy fast?

(1) Arctic terns nest in the far north. (2) Terns are light, with long, narrow wings. (3) They can hover over water. (4) They dive for small fish. (5) One tern flew over 40,000 miles in a year. Sentence 5 shows terns fly far. Which adds a second support?

(1) Corals host tiny algae. (2) The algae make food for the coral. (3) Some corals glow. (4) When water stays too warm, corals push the algae out. (5) Corals eat plankton too. Sentence 2 hints a pale coral can starve. Which adds a second support?

(1) The statue's skin is thin copper. (2) A steel frame holds it up. (3) Its torch is coated in gold. (4) Souvenir copies are green plastic. (5) Damp air turns copper green. Sentence 1 hints the green comes from the metal. Which adds a second support?

(1) The Colorado carries sand and gravel. (2) The walls show rock layers. (3) The grains scrape and cut the riverbed. (4) The walls rise a mile high. (5) The layers formed long ago. Sentence 1 hints the river carved the canyon. Which adds a second support?