A.Tobacco smoking can cause life-shortening diseases.
B.There are twice as many men smokers as women smokers in the U. S. According to the 1970 figures.
C.Filters can only decrease rather than eliminate the harm to the human body.
D.In the smoke there is nicotine which is an important factor in the development of cancer of some organs.

42、(同41题)The statement "be associated with a shortened life expectancy" in the s***nd aragraph signifies____

A.\!cause a life expectancy to shorten".
B.\!be caused by a shortened life expectancy".
C.\!will change with the shortened life expectancy".
D.\!will cause from the shortened life expectancy".

43、(同41题)Female smokers are probably less affected by heart disease because____

A.cigarettes women smoke are treated in a special way.
B.tissue of the heart can get rid of the poisonous elements.
C.they inhale the smoke less deeply.
D.they, in most cases, pretend to be smokers.

44、(同41题)Tobacco smoke is a mixture____

A.of two poisonous elements.
B.of various poisonous substances.
C.of some irritant gases.
D.of carbon dioxide and water vapour.

45、(同41题)Harmfulness from all forms of smoking to the human body may be arranged in severity sequence as follows:____

A.Cigarette smoking is put first, and next comes cigar or pipe smoking.
B.No 1 killer is cigar smoking, and it’s followed by cigarette or pipe smoking.
C.Cigar or pipe smoking has nearly no effect on the human body in contrast with igarette smoking.
D.All forms of smoking are similar in effect harmful to the human body.

46、Vision。 I____。Vision is physiological power of sight. Vision is the faculty by which, th rough the material organ, the eye, the visible external world is perceived. Many simple organisms have light receptors and can thus react to motion and shadows, but true vision involves the formation of images in the brain. Eyes of differen t organisms provide images of varying clarity: This article deals with vision in humans and other animals with eyes of comparable complexity.

47、Basic P____。On ordinary optical principles, a point above the direct line of vision co mes to a focus at a point of the retina below its center, and vice versa. If a r etina were observed by another person, the observer would see that the image of an object is formed on the retina, and that this image is inverted. Any increase in the magnitude of the retinal image is generally associated with approach of the object; if this same result is brought about by means of lenses, however-eve n where the real distance is increased-the object still seems to approach. This seeming approach is the result of an unconscious process of reasoning. The mind interprets any given object as being of a known or ascertained size.
48、Sight D____。The most common disturbance to vision is caused by crystals or other small opaque bodies in the humors of the eye, which are usually only a passing inconv enience. Much more serious are opacities called cataracts, which develop in the lens as a result of mechanical injury, advancing age, or dietary deficiencies. O pacity of the cornea also causes obscured vision, but this condition may be repa ired through transplantation of a section of clear cornea from another person.