Questions 11-19
v$ U6 G$ d6 m3 p% f. eThe origins of nest-building remain obscure, but current observation of nest-building
7 h8 E* x0 c' Zactivities provide evidence of their evolution. Clues to this evolutionary process can be
9 M7 s. f7 J" \$ Z1 Zfound in the activities of play and in the behavior and movements of birds during mating,; f$ x5 ^2 \8 M$ q% K6 t
Line such as incessant pulling at strips of vegetation or scraping of the soil. During the early
6 z* Y! `2 B$ W(5) days of the reproductive cycle, the birds seem only to play with the building materials. In
! o3 ]- H6 t3 \% P; v8 s4 `preparation for mating, they engage in activities that resemble nest-building, and continue8 y/ C, L, P9 y$ [" C, p
these activities throughout and even after the mating cycle. Effective attempts at construction
+ j7 \% ^( o3 |( u3 o7 M) ~occur only after mating.4 p: Q( b! j5 b
Although nest-building is an instinctive ability, there is considerable adaptability in
/ p9 I8 o4 U9 |" `- w(10) both site selection and use of materials, especially with those species which build quite
. Z% V7 x( [- p- D6 @; `4 a xelaborate constructions. Furthermore, some element of learning is often evident since
# C- ~5 e8 ?) S" s$ U: Lyounger birds do not build as well as their practiced elders. Young ravens, for example,8 f" {$ M( H, y u& F
first attempt to build with sticks of quite unsuitable size, while a jackdaw's first nest
# m6 z% x/ {3 [5 Kincludes virtually any movable object. The novelist John Steinbeck recorded the contents
* n' z; G1 ^; r5 B' Q" q/ t(15) of a young osprey nest built in his garden, which included three shirts, a bath towel, and
3 k; T3 M/ J- I/ A# K$ c" t+ A2 i( i! ?6 Lone arrow.
& {, F, S. @& E% \( g5 m$ ?8 l2 dBirds also display remarkable behavior in collecting building materials. Crows have+ X, Q- F$ h( U& C+ U
been seen to tear off stout green twigs, and sparrowhawks will dive purposefully onto a! g Z& b* G* K! b" \, @' X
branch until it snaps and then hang upside down to break it off. Golden eagles, over
* r& B- b$ N$ b! n(20) generations of work, construct enormous nests. One of these, examined after it had been
; Z7 j7 f: a; {* [' [9 fdislodged by high winds, weighed almost two tons and included foundation branches% T; f4 j) V" v
almost two meters long. The carrying capacity of the eagles, however, is only relative to8 B& M7 ^, Z+ U+ ^
their size ant1 most birds are able to carry an extra load of just over twenty percent of their* t8 y" l! D* c1 u% j" [/ B# S
body weight. _6 p4 K2 S: G6 O3 i" U6 o0 u) L
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11. The word "obscure" in line 1 is closest in meaning to" m* |5 r! m: M+ P0 }0 ^, d3 F
(A) interesting
( m4 }) s& O: \8 _2 M(B) unclear
3 m( x; C" ]3 k+ s+ T(C) imperfect$ G& y, H) d" V
(D) complex9 O1 K; t/ @8 Z! o% x5 H" ]8 \
& Z4 E, f; k# {- t12. According to the passage, which of the following activities is characteristic of the early part of the reproductive cycle of birds?# L! g8 }7 |$ f' t* h1 i
(A) Selecting a mate
2 L( g4 h# v6 e* H% N(B) Collecting nest-building materials
- {- |2 b1 x! I x/ B4 n: v% T+ {(C) Playing with nest-building materials2 x( | F q' i
(D) Building a nest |