Until the middle of the nineteenth century, most Americans were indifferent to paint. Wood was plentiful and cheap especially on the frontier; (21)——most settlers had to chop down trees to dear theîr land. (22)— eager to start farming, they used their wood to build their cabins as cheaply and quickly as possible. If they had painted their buildings, this (23) — their durability;(24) — painting was an expensive and timeconsuming job. There were (25) ——more urgent calls upon their time and their money.
21.
A) on the contrary
B) as if
C) similarly
D) in case
E) in fact

22.
A) Having been
B) To be
C) To have been
D) Being
E) Having to be

23.
A) had extended
B) might have extended
C) vas extending
D) would be extending
E) might extend

24.
A) but
B) whether
C) unless
D) that
E) if

25.
A)none
B) any
C) anywhere
D) other
E)so

A) a species bank of captive cranes has been created to guard against extinction
B) some cranes depend exclusively upon wetlands for nesting and feeding
Of any effort to protect them requires theparticipation of severaı countries
D) an International effort to ensure safe passage for cranes would have been hardly feasible
E) this was simply a means to draw global attention to cranes and their work

27. — where farmers benefit from legal opium cultivation for the production of painkillers.
A) Turkey is one of several countries
B) The UN's drugcontrol agency admits that cropsubstitution projects are inadequate
Ç) Total opium elimination in these countries is hardlyfeasible
D) Until recently, only the trafficking of opium was prohibited in Laos, not the cultivation of it
E) Opium is one of the oldest painkillers known

28. —, when Eveready introduced the alkallne battery.
A) Their technological success is stili being guestioned
B) Many new materials have been adapted for battery use
C) Mercury, too, has recently been eliminated from batteries on account of its toxicity
D) The lifespans of these batteries are expected to improve
5) The first major advance in flashlight batteries came in 1959

29. — that New York City is being badly run and desperately needs to be reorganized.
A) None of them had admitted
B) Everybody acknovwledges
C) Many Americans were asking the authorities
D) Letters of protest had been written to the Mayor's Office
E) Many journallsts would recommend

30. Because scientists believe that comets in the distant past deposited water and organic compounds on both Earth and its moon
A) in the 1990s, two probes that orbited the moon raised new guestions about Earth's airless satellite
B) it is the largest impact crater in the entire solar system
C) the exploration agenda would have been changed
D) wellpreserved ice at the lunar poles could yield clues to the origins of life
E) those lunar missions had been supported by very few scientists