319. An acre originally represented the area that a yoke of oxen _____ in a single day.
a. a plow
b. to plow
c. plowing
d. could plow

320. _____ the chemicals that make water hard.
a. For carbonites to be
b. Carbonites are
c. Carbonites
d. In carbonites

321. _____ that we see is made up of all the colors of the spectrum.
a. In the light
b. The light
c. It lights
d. Because the light

322. Only beryl _____ deep green in color can be called emerald.
a. that is
b. is
c. it is
d. that

323. Unlike paints, _____ into the material that they color.
a. dyes dispersing
b. the dispersion of dyes
c. dyes are dispersed
d. to disperse dyes

324. A baseball _____ a cork and rubber core that is tightly wrapped with yarn.
a. which has
b. having
c. it has
d. has

325. The muscle that the fiddler crab uses to pull its pincer shut _____.
a. with extreme strength
b. must be extremely strong
c. it must be extremely strong
d. extreme strength

326. The Thirteenth Amendment to the Constitution, which _____, was proclaimed on December 18, 1865.
a. abolishing slavery
b. slavery to abolish
c. the abolition of slavery
d. abolished slavery

327. President Herbert Hoover, for whom _____, was educated as an engineer.
a. Hoover Dam’s name
b. the name of Hoover Dam
c. Hoover Dam was named
d. naming Hoover Dam

328. _____, which formed in the crater of an extinct volcano, is the deepest lake in the United States.
a. In Crater Lake
b. Crater Lake is a lake
c. Crater Lake
d. The lake has a crater

329. _____ in which most carnivorous plants live do not provide the plants with enough nourishment.
a. The poor soils
b. Within the poor soils
c. The soils are poor
d. The poor soils are

330. Most tundra plants are mosses and lichens _____ the ground for warmth.
a. that hug
b. hug
c. they hug
d. that a hug

331. In 1705, Edmond Halley, for whom Halley’s Comet is named, _____ the 1758 return of the comet.
a. accurate prediction
b. prediction with accuracy
c. he predicted accurately
d. accurately predicted

332. George Washington’s _____ on the balcony of the Federal Hall in New York City, which was then the national capital.
a. the place of the inauguration
b. inauguration took place
c. was inaugurated in a place
d. took the place of an inauguration

333. _____ of serving lemon with fish derived from the belief that the acid in lemon juice would dissolve fish bones.
a. The custom
b. Because it is customary
c. It is customary
d. The custom is

334. Pandas have a thumb-like sixth finger _____ really an extension of the wrist bone.
a. is
b. it is
c. which
d. which is

335. Hawks have excellent eyesight that they _____ even tiny prey on the ground from high in the air.
a. using to spot
b. to spot a use
c. use to spot
d. a use on spots

336. Keno, an early form of bingo, _____ of chance which dates from the early nineteenth century.
a. it is a game
b. which is a game
c. is a game
d. a game

337. The first reigning king for whom the U.S. _____ an official reception was David Kalakaua, king of the Sandwich Islands.
a. government’s hold
b. government held
c. the hold of the government
d. holding the government

338. The people who _____ in North America during colonial times commonly ate cornmeal mush or boiled rice for breakfast.
a. settled
b. settling
c. to settle
d. the settlement