13.According to the passage， helium is

　　（A） the second-most abundant element in the universe

　　（B） difficult to detect

　　（C） the oldest element in the universe

　　（D） the most prevalent element in quasars

　　14.The word "constituents" in line 9 is closest in meaning to

　　（A） relatives

　　（B） causes

　　（C）components

　　（D） targets

　　15.Why does the author mention "cosmic rays t in line 10？

　　（A）As part of a list of things containing helium

　　（B）As an example of an unsolved astronomical puzzle

　　（C） To explain how the universe began

　　（D） To explain the abundance of hydrogen in the universe

　　16.The word "vary" in line 14 is closest ill meaning to

　　（A） mean

　　（B） stretch

　　（C） change

　　（D） include

　　17.The creation of helium within stars

　　（A） cannot be measured

　　（B） produces energy

　　（C） produces hydrogen as a by-product

　　（D） causes helium to be much more abundant In old stars than In young star：

　　18. The word "calculated" in line 20 is closest in meaning to

　　（A） ignored

　　（B） converted

　　（C） increased

　　（D） determined

　　19.Most of the helium in the universe was formed

　　（A） in interstellar space

　　（B） in a very short time

　　（C）during the first minute of the universe s existence

　　（D） before most of the hydrogen

　　20.The word "ceased" in line 35 is closest in meaning to

　　（A）extended

　　（B）performed

　　（C）taken hold

　　（D）stopped

　　Questions 21-30

　　In colonial America， people generally covered their beds with decorative quilts resembling those of the lands from which the quitters had come. Wealthy and socially prominent settlers made quilts of the English type， cut from large lengths of cloth of the same color and texture rather than stitched together from smaller pieces. They mad these until the advent of the Revolutionary War in I 775， when everything English came to be frowned upon.