2. A。 分析：借助空格所在的結(jié)構(gòu)（。。主要的作用力被知道的很少）判斷A（關(guān)于）合適。
3． A)waits for B)longs for C)accounts for D)looks for
Astronomers now know that luminous matter-stars, planets and hot gas – _3_ only about 0.4 percent of the universe．Non．1uminous components．such as black holes and intergalactic gas，make up 3.6 percent．The rest is either dark matter, about 23 percent，or dark energy, about 73 percent．
3。C. 分析：借助空格所在的局部結(jié)構(gòu)的內(nèi)容“行星和熱的氣體。。只有宇宙的0。4”判斷C（v.說明, 占）合適。long for v.渴望
4． A)schedule B)time C)duration D)period
Dark matter, sometimes called “cold dark matter,” has been known for some _4_.
4． B。 分析：被選項在含義上都與“時間”有關(guān)系。借助空格所在的搭配結(jié)構(gòu)“已經(jīng)被知道。?！迸袛郆合適（（一段）時間）。
Period的用法是通常該詞的前面要帶修飾語，如：
a short waiting period 等了一小會兒；
one of the most difficult periods of her life她生命中最困難的時期；
或者是for a period of這樣的結(jié)構(gòu)
worked for a period of ten years工作了十年時間；
duration強調(diào)“持續(xù)時期”，與 for 搭配的結(jié)構(gòu)是“for the duration”/ 在整段時間內(nèi)
5． A)displayed B)delayed C)relayed D)played
Only recently have researchers come to understand the pivotal role it _5_ in the formation of stars, planets and even people．
5．D．分析：空格前出現(xiàn)了role，在role的后面是一個句子對role進(jìn)行說明（定語從句），而這個定語從句與role有關(guān)，所以判斷D是答案：play the/a role in ../在..方面起作用。定語從句的含義是“它在星星，行星甚至人的形成上所起的（關(guān)鍵性的作用）”
display vt.陳列, 展覽, 顯示 n.陳列, 展覽, 顯示
delay v.耽擱, 延遲, 延期 n.耽擱, 延遲
relay vt.(消息, 貨物等)分程傳遞, 轉(zhuǎn)播
6． A)previously B)back C)before D)ago
“We owe our very existence to dark matter,” said physicist Paul Steinhardt and a co-author of a review on dark matter which appeared not long _6_ in the journal Science．
1． D。 分析：借助空格所在的局部搭配結(jié)構(gòu)“not long ”和謂語部分的時態(tài)—一般過去時態(tài)，判斷D是答案。
7． A)beginning B)changing C)combining D)ending
3． A)waits for B)longs for C)accounts for D)looks for
Astronomers now know that luminous matter-stars, planets and hot gas – _3_ only about 0.4 percent of the universe．Non．1uminous components．such as black holes and intergalactic gas，make up 3.6 percent．The rest is either dark matter, about 23 percent，or dark energy, about 73 percent．
3。C. 分析：借助空格所在的局部結(jié)構(gòu)的內(nèi)容“行星和熱的氣體。。只有宇宙的0。4”判斷C（v.說明, 占）合適。long for v.渴望
4． A)schedule B)time C)duration D)period
Dark matter, sometimes called “cold dark matter,” has been known for some _4_.
4． B。 分析：被選項在含義上都與“時間”有關(guān)系。借助空格所在的搭配結(jié)構(gòu)“已經(jīng)被知道。?！迸袛郆合適（（一段）時間）。
Period的用法是通常該詞的前面要帶修飾語，如：
a short waiting period 等了一小會兒；
one of the most difficult periods of her life她生命中最困難的時期；
或者是for a period of這樣的結(jié)構(gòu)
worked for a period of ten years工作了十年時間；
duration強調(diào)“持續(xù)時期”，與 for 搭配的結(jié)構(gòu)是“for the duration”/ 在整段時間內(nèi)
5． A)displayed B)delayed C)relayed D)played
Only recently have researchers come to understand the pivotal role it _5_ in the formation of stars, planets and even people．
5．D．分析：空格前出現(xiàn)了role，在role的后面是一個句子對role進(jìn)行說明（定語從句），而這個定語從句與role有關(guān)，所以判斷D是答案：play the/a role in ../在..方面起作用。定語從句的含義是“它在星星，行星甚至人的形成上所起的（關(guān)鍵性的作用）”
display vt.陳列, 展覽, 顯示 n.陳列, 展覽, 顯示
delay v.耽擱, 延遲, 延期 n.耽擱, 延遲
relay vt.(消息, 貨物等)分程傳遞, 轉(zhuǎn)播
6． A)previously B)back C)before D)ago
“We owe our very existence to dark matter,” said physicist Paul Steinhardt and a co-author of a review on dark matter which appeared not long _6_ in the journal Science．
1． D。 分析：借助空格所在的局部搭配結(jié)構(gòu)“not long ”和謂語部分的時態(tài)—一般過去時態(tài)，判斷D是答案。
7． A)beginning B)changing C)combining D)ending