[单项选择]Medical scientists believe that
A. tests have been designed to settle the cholesterol dispute
B. drugs have been tested to reduce the amount of the substance in blood
C. low cholesterol foods or anti-cholesterol drugs or both can reduce the chance of a heart attack
D. none of the statements mentioned above is correct

[单项选择]Medical scientists believe that______.
A. tests have been designed to settle the cholesterol dispute
B. drugs have been tested to reduce the amount of the substance in blood
C. low cholesterol foods or anti-cholesterol drugs or both can reduce the chance of a heart attack
D. none of the statements mentioned above is correct

[单项选择]Political scientists believe that the important cause for decreasing voter turnout is ______.
A. the inconvenience of voting
B. the commercialization of the voting procedures
C. the lack of interest and enthusiasm in politics
D. the insecurity of voting on line due to the constant breakdown of computer systems

[单项选择]Scientists believe that there is not enough oxygen in the Moon's atmosphere to______ plant life.
A. adapt
B. personalize
C. sustain
D. describe

[单项选择]Some scientists believe that there is no evidence that cholestrol in food is directly linked to ______.
A. blood disease
B. heart disease
C. infectious disease
D. mental disorder

[单项选择]Some scientists believe that a breakthrough in the use of solar energy depends on _________.
A. advanced technology
B. further experiments
C. sufficient funding
D. well-equipped laboratories

[单项选择]Some scientists believe that dolphins have a language of their own.

[单项选择]Some scientists believe that global warming could（　）.
A. modify ocean currents.
B. change wind directions in the polar regions.
C. reduce the influence of currents.
D. increase wind speed.

[单项选择]Scientists believe that when life on earth began, the earth atmosphere consisted of ___________.
A. oxygen and nitrogen
B. hydrogen, oxygen and nitrogen
C. hydrogen and its compounds
D. hydrogen, oxygen and their compounds

[单项选择]

Scientists believe that people "dressed up" long before they made a habit of wearing clothes. Primitive man dressed himself in feathers and ornaments, or painted his body and wrapped himself in animal skins. It was probably some time before man discovered that the decorations kept him warm and protected him from-various injuries. Even today, millions of people who wear little clothing use ornaments and decorations.
When primitive people began to wear clothing regularly, they had to make it from the materials at hand, In cold regions, they often used the skins of fur-bearing animals as protection against the cold. In warmer regions of the world, the people dressed themselves in clothing made from leaves, tree bark and woven grasses. Some people scraped the hair from animal skins to make soft leather for their clothes.
Linen was the first woven material from which clothes were made. From very early times, men have known how to make flax into fine linen. In
A. Sheep can be raised easily and can live in varied climates.
B. Linen was difficult to produce.
C. People liked to wear wool.
D. Fine linen only could be worn by rich people.

[单项选择]Scientists believe that human evolution ______.
A. has seldom been accompanied by climatic changes
B. has exerted little influence on climatic changes
C. has largely been effected by climatic changes
D. has had a major impact on climatic changes