Questions 11-19
" a: \5 M9 ?5 n$ l6 s E3 KThe origins of nest-building remain obscure, but current observation of nest-building
. }& M) R+ W* } d, V' a# W+ X5 J3 factivities provide evidence of their evolution. Clues to this evolutionary process can be
) R) n# A0 ~" n+ Nfound in the activities of play and in the behavior and movements of birds during mating,8 w6 S' k: V) _* c H! t
Line such as incessant pulling at strips of vegetation or scraping of the soil. During the early5 C/ q& N( E8 n. a; M
(5) days of the reproductive cycle, the birds seem only to play with the building materials. In
" G9 G- Z2 G$ F3 Y2 J* D/ fpreparation for mating, they engage in activities that resemble nest-building, and continue
5 O) {; I1 V' g" [. N8 Tthese activities throughout and even after the mating cycle. Effective attempts at construction8 u5 E4 g# f8 i' h# [2 Z) a" t
occur only after mating.
- h6 i+ I: O/ OAlthough nest-building is an instinctive ability, there is considerable adaptability in
# r: K6 X; U; v! C- ^' \1 u% `(10) both site selection and use of materials, especially with those species which build quite
g4 ~1 G% `. d( j# O1 L: ?4 N& V! |elaborate constructions. Furthermore, some element of learning is often evident since8 o5 f; H3 P5 f, S
younger birds do not build as well as their practiced elders. Young ravens, for example,
' K, N7 s* D' t) Efirst attempt to build with sticks of quite unsuitable size, while a jackdaw's first nest
* P$ H1 P! G6 I, x jincludes virtually any movable object. The novelist John Steinbeck recorded the contents0 W- c1 J1 B6 Z% N$ S" P0 y
(15) of a young osprey nest built in his garden, which included three shirts, a bath towel, and6 c& D8 O. U2 @( z
one arrow.
: T: R: _0 ?" C5 l! R/ aBirds also display remarkable behavior in collecting building materials. Crows have
# d2 [0 R5 B! {( kbeen seen to tear off stout green twigs, and sparrowhawks will dive purposefully onto a( t. Z2 F0 h( A) y2 E
branch until it snaps and then hang upside down to break it off. Golden eagles, over+ y* Z1 y" [% i! M: N9 m; h
(20) generations of work, construct enormous nests. One of these, examined after it had been" s! ^& S% s# T1 ]
dislodged by high winds, weighed almost two tons and included foundation branches0 V" n1 O. X- C7 C8 I
almost two meters long. The carrying capacity of the eagles, however, is only relative to
6 E2 [# c- H: U+ v3 M6 xtheir size ant1 most birds are able to carry an extra load of just over twenty percent of their
4 M- v* E' u# o/ R' ybody weight.
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' i" e) b/ h9 G6 r- V7 G11. The word "obscure" in line 1 is closest in meaning to
, C a/ f& ^. ~) g(A) interesting
* j# N" g3 v _( Z(B) unclear8 G' t4 b6 n( g2 l2 }
(C) imperfect
* n( A/ V, ^& t; Q+ _( d& C- V; H(D) complex
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% _9 B9 B) k; k( p12. According to the passage, which of the following activities is characteristic of the early part of the reproductive cycle of birds?
# V; k0 d0 ^1 y) b* s# D(A) Selecting a mate
! h, I) k$ k/ ^. C J(B) Collecting nest-building materials7 B; W6 x! ^8 u# G; c/ T: G
(C) Playing with nest-building materials% b) \1 }: R; g! F1 G; X% |
(D) Building a nest |