13.According to the passage, helium is (A) the second-most abundant element in the universe * O2 D7 [* c# b9 ] \5 f (B) difficult to detect ) A( _5 [- n) |' v* @* l- `; k (C) the oldest element in the universe * N" l: ?. a+ A& m# m6 g9 j (D) the most prevalent element in quasars4 d& Q9 n/ N: H
14.The word "constituents" in line 9 is closest in meaning to% O0 w# d" g+ Z: O E1 l2 Z
(A) relatives" Q7 }" }, L+ Q; C4 i6 L b
(B) causes- [% o: L5 D# m9 A+ j) S
(C)components % S- e Y$ g+ m+ C f- I (D) targets 9 E0 E1 f$ C8 N* r' R% I# U 15.Why does the author mention "cosmic rays t in line 10? + D; T: ]( c* Z# B (A)As part of a list of things containing helium 9 y& p: D1 K6 A5 U' H: i& H$ G [ (B)As an example of an unsolved astronomical puzzle; j4 Z' P% ~ G7 Q% x! V4 J
(C) To explain how the universe began 4 k' [8 y8 Z/ M (D) To explain the abundance of hydrogen in the universe H. n3 d6 H2 z7 A9 ^; Q 16.The word "vary" in line 14 is closest ill meaning to; F% \& U9 B& f1 D
(A) mean9 E% p9 z, O0 r& J
(B) stretchwww.examw.com ) m2 T( ~+ X/ o: a" o6 P (C) change5 x$ \* z2 ~$ l+ l- P8 D
(D) include 1 \- w4 v+ d& b# @2 | ^) j 17.The creation of helium within stars4 ]2 a# V3 l( A+ k
(A) cannot be measured $ k% i2 Y2 L. Y- h (B) produces energy: s3 f" b* d8 M2 l5 `9 p
(C) produces hydrogen as a by-product 6 E, s3 K w! Q( N- H (D) causes helium to be much more abundant In old stars than In young star: