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A thousand-li journey is started by taking the first step.以下是店铺为大家搜索整理的托福英语阅读每日精选一练，希望能给大家带来帮助!
Perhaps one of the most dramatic and important changes that took place in the Mesozoic era occurred late in that era, among the small organisms that populate the uppermost, sunlit portion of the oceans — the plankton. The term "plankton" is a broad one, designating all of the small plants and animals that float about or weakly propel themlves through the a. In the late stages of the Mesozoic era, during the Cretaceous period, there was a great expansion of plankton that precipitated skeletons or shells compod of two types of mineral: silica and calcium carbonate.
This development radically changed the types of diments that accumulated on the afloor, becau, while the organic parts of the plankton decayed after the organisms died,
their mineralized skeletons often survived and sank to the bottom. For the first time in the Earth's long history, very large quantities of silica skeletons, which would eventually harden into rock, began to pile up in parts of the deep a. Thick deposits of calcareous ooze made up of the tiny remains of the calcium carbonate-creting plankton also accumulated as never before. The famous white chalk cliffs of Dover, in the southeast of England, are just one example of the huge quantities of such material that amasd during the Cretaceous period; there are many more. Just why the calcareous plankton were so prolific during the latter part of the Cretaceous period is not fully understood. Such massive amounts of chalky diments have never since been deposited over a comparable period of time.
The high biological productivity of the Cretaceous oceans also led to ideal conditions for oil accumulation. Oil is formed when organic material trapped in diments is slowly buried and subjected to incread temperatures and pressures, transforming it into petroleum. Sediments rich in organic material accumulated along the margins of the Tethys Seaway, the tropical east-west ocean that formed when Earth's single landmass (k
nown as Pangaea) split apart during the Mesozoic era. Many of today's important oil fields are found in tho diments — in Russia, the Middle East, the Gulf of Mexico, and in the states of Texas and Louisiana in the United States.
1. What does the passage mainly discuss?
(A) How diments were built up in oceans during the Cretaceous period
(B) How petroleum was formed in the Mesozoic era
(C) The impact of changes in oceanic animal and plant life in the Mesozoic era
(D) The differences between plankton found in the prent era and Cretaceous plankton
2. The passage indicates that the Cretaceous period occurred
(A) in the early part of the Mesozoic era
(B) in the middle part of the Mesozoic era
(C) in the later part of the Mesozoic era
(D) after the Mesozoic era
3. The passage mentions all of the following aspects of plankton EXCEPT
(A) the length of their lives
(B) the level of the ocean at which they are found
(C) their movement
(D) their size
4. The word "accumulated" in line 8 is clost in meaning to
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(A) depended
(B) matured
(C) dissolved
(D) collected
5. According to the passage , the most dramatic change to the oceans caud by plankton during the Cretaceous period concerned
(A) the depth of the water
(B) the makeup of the diment on the ocean floor
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(C) the decrea in petroleum-producing diment
(D) a decline in the quantity of calcareous ooze on the afloor
6. The "white chalk cliffs of Dover" are mentioned in line 14 of the passage to
(A) show where the plankton diment first began to build up
(B) provide an example of a plankton buildup that scientists cannot explain
(C) provide an example of the buildup of plankton diment
却话巴山夜雨时上一句(D) indicate the largest single plankton buildup on Earth
7. The word "prolific" in line 17 is clost in meaning to
(A) fruitful
(B) distinct
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(C) determined
(D) energetic
8. The word "ideal" in line 20 is clost in meaning to
雪景的句子(A) common
笑谈大先生(B) clear
(C) perfect
(D) immediate
9. The word "it" in line 22 refers to
(A) biological productivity
(B) oil
(C) organic material
(D) petroleum
参考答案：
CBBAA DCACC
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