Everyone dreams about 20 percent of their sleeping time. 23 people who say they never dream show about 20 percent of REM sleep. 24 these “non-dreamers” do their sleeping in a laboratory 25 researchers can wake them up and ask them whether they were having dreams the moment before, it 26 that they dream as much as others.
答案：(A) If
條件句「如果這些不做夢的人在實驗室睡覺，研究人員就能叫醒他們」，If 引導條件子句；No matter（通常接疑問詞構成讓步子句，不能單獨這樣用）、No wonder（難怪）、Although（雖然，轉折）都不合。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
四個選項擺進句首唸起來都不算突兀，而 Although（雖然）與 If（如果）在中文裡又常常被混著用，於是很容易在這兩個之間憑感覺挑。這一格有一個形態上的破綻可以先砍掉一半。
先看結構：空格後面是一個完整的子句（these non-dreamers do their sleeping in a laboratory ...），逗號之後 it turns out that they dream as much as others 又是一個完整的主要子句。兩個完整子句要接在一起，空格要的是從屬連接詞。No matter 先出局——它不能單獨帶子句，一定要接一個 wh- 詞才成立（no matter how、no matter what、no matter who）。No wonder 也出局——它的意思是「難怪」，完整說法是 It is no wonder that ...，它自己屬於主要子句的一部分，不是帶條件的連接詞。剩下 If 與 Although，這時才用語意分：「讓這些人在實驗室裡睡覺、研究人員可以叫醒他們」與「結果發現他們做夢做得跟別人一樣多」之間是條件與結果的關係——先設定這個條件，才會得到那個發現，不是「雖然……但是……」的讓步，所以填 If。
Although（雖然）：讓步要求前後兩件事互相牴觸，但本句前後是順著走的（做了這個實驗，所以得到這個結果），沒有牴觸。No matter（無論）：形態不完整，要接 wh- 詞。No wonder（難怪）：不是從屬連接詞，接不出「條件子句加主要子句」這個結構。
in a laboratory（在實驗室裡）、wake sb up（叫醒某人）、ask sb whether …（問某人是否……）、as long as（只要，表條件）、no matter how（無論如何）、as much as（和……一樣多）。
Basically, there are two kinds of sleep. One is Rapid Eye Movement (REM) sleep. In 21 , the brain waves of a sleeping person are similar to those of a waking person, and the eyes move about rapidly under the closed lids. 22 kind of sleep is Non-Rapid Eye Movement sleep.
Scientists have discovered that dreams happen mainly in REM sleep. Everyone dreams about 20 percent of their sleeping time. 23 people who say they never dream show about 20 percent of REM sleep. 24 these "non-dreamers" do their sleeping in a laboratory 25 researchers can wake them up and ask them whether they were having dreams the moment before, it 26 that they dream as much as others.
Events in daily life sometimes occur symbolically in dreams. 27 , a boy is having difficulties on the school playground because a bigger boy keeps bullying him. He may dream at night of being alone in the playground, 28 a lion. At other times the dreaded event from daily life simply occurs in a dream in its real-life form; 29 , the boy dreams of being bullied by the bigger boy.
30 scientific research, we have known more about the relationship between sleep and dreams. However, why a dream will take a certain symbolic form is still a mystery.