Substances suspected of causing cancer, if carefully administered to experimental animals in quantities in which those substances are ordinarily present in the environment, are virtually guaranteed not to produce cancer at rates significantly above the chance levels. The most economical procedure for obtaining informative data is to administer vastly increased amounts of the substance being tested.
The economical procedure described above will not be an effective one if which of the following is true?
(A) Cancer data on experimental animals yield accurate estimates of the risk of cancer for human beings.
(B) Experimental animals will often develop cancer in response to receiving excessive quantities of a substance regardless of the specific properties of the substance.
(C) When more of a possibly cancer causing substance is administered to experimental animals fewer animals are needed for significant data to be obtained.
(D) Among experimental animals the chance levels for many types of cancer is virtually zero.
(E) Substances will virtually be tested in amounts greater than necessary to obtain informative data作者: nil1989 时间: 2002-11-11 14:23
应该不是B,如果B对，那么应该改成regardless of the specific AMOUNTS of the substance.关键是致癌物质的数量，而不是致癌物质的特性。
