13.According to the passage， helium is （A） the second-most abundant element in the universe
. J% ~) Q0 U- ^! s% y （B） difficult to detect
" h$ w5 H% v* y5 h! N （C） the oldest element in the universe! e1 I+ U( H( Y v1 ]) K9 f
（D） the most prevalent element in quasars
$ Q" }& [$ I2 E0 ~/ j2 x9 P4 Q0 P 14.The word "constituents" in line 9 is closest in meaning to2 o# X3 q# u$ w( B
（A） relatives
, o @* W+ W+ v1 O4 N# a （B） causes- O! h& F/ {; _* E! b" }
（C）components
. j h; F6 w4 C- X1 U （D） targets
g! {' h% r/ K8 p& T7 Z 15.Why does the author mention "cosmic rays t in line 10？
; e8 K4 K2 t6 b* `! s+ l （A）As part of a list of things containing helium; P1 b. m# {: o$ ~$ j+ Y( K% r: E) Q
（B）As an example of an unsolved astronomical puzzle. I* o7 ]* n1 v
（C） To explain how the universe began
( d6 F6 _, d4 c- Y5 j （D） To explain the abundance of hydrogen in the universe1 o! q8 |% L+ v! I( u% i
16.The word "vary" in line 14 is closest ill meaning to& l5 P7 G+ k+ q& ]- |* R
（A） mean
4 K- s: [8 }# } n （B） stretchwww.examｗ.com
# n F3 N) n( b2 w% n9 E （C） change: @' D4 W+ h1 W( \* }0 p+ f
（D） include
# p, @# g, K$ g+ w$ W8 g, I 17.The creation of helium within stars9 y, J1 h' y% F0 H- b
（A） cannot be measured: Z( f7 F% K% ^2 p# K
（B） produces energy
) @6 S8 v) H. |7 R （C） produces hydrogen as a by-product
. x+ M" K b& s [6 U# d （D） causes helium to be much more abundant In old stars than In young star： |
发表于 2012-8-14 22:15:45
