24. The passage tells us that the most probable reason for the death of the mice in Ader's experiment was that .

　　A) the sweetener was poisonous to them

　　B) their immune systems had been altered by the mind��

　　C) they had been weakened psychologically by the saccharin��

　　D) they had taken too much sweetener during earlier conditioning

　　25. It can be concluded from the passage that the immune systems of animals .

　　A) can be altered by electric shocks

　　B) can be weakened by conditioning

　　C) can be suppressed by drug injections

　　D) can be affected by frequent doses of saccharin

　　Questions 26 to 30 are based on the following passage:

　　The destruction of our natural resources and contamination of our food supply continue to occur, largely because of the extreme difficulty in affixing (把……固定) legal responsibility on those who continue to treat our environment with reckless abandon (放任). Attempts to prevent pollution by legislation, economic incentives and friendly persuasion have been met by lawsuits, personal and industrial denial and long delays—not only in accepting responsibility, but more importantly, in doing something about it. It seems that only when government decides it can afford tax incentives or production sacrifices is there any initiative for change. Where is industry's and our recognition that protecting mankind's great treasure is the single most important responsibility? If ever there will be time for environmental health professionals to come to the frontlines and provide leadership to solve environmental problems, that time is now.

　　We are being asked, and, in fact, the public is demanding that we take positive action. It is our responsibility as professionals in environmental health to make the difference. Yes, the ecologists, the environmental activists and the conservationists serve to communicate, stimulate thinking and promote behavioral change. However, it is those of us who are paid to make the decisions to develop, improve and enforce environmental standards, I submit, who must lead the charge. We must recognize that environmental health issues do not stop at city limits, county lines, state or even federal boundaries. We can no longer afford to be tunnel-visioned in our approach. We must visualize issues from every perspective to make the objective decisions. We must express our views clearly to prevent media distortion and public confusion. I believe we have a three-part mission for the present. First, we must continue to press for improvements in the quality of life that people can make for themselves. Second, we must investigate and understand the link between environment and health. Third, we must be able to communicate technical information in a form that citizens can understand. If we can accomplish these three goals in this decade, maybe we can finally stop environmental degradation, and not merely hold it back. We will then be able to spend pollution dollars truly on prevention rather than on bandages.��

　　26. We can infer from the first two paragraphs that the industrialists disregard environmental protection chiefly because .

　　A) it is difficult for them to take effective measures

　　B) time has not yet come for them to put due emphasis on it

　　C) they are reluctant to sacrifice their own economic interests

　　D) they are unaware of the consequences of what they are doing