4. In response to experimental results concerning IBMX（最后一段）, Snyder et al contended that it is not uncommon*4 for psychoactive drugs to have
(A) mixed effects in the brain*4A
(B) inhibitory effects on enzymes in the brain
(C) close structural relationships with caffeine
(D) depressive effects on mouse locomotion（A）
(E) the ability to dislodge caffeine from receptors in the brain
5. The passage suggests that Snyder et al believe that if the older theory concerning caffeine’s effects were correct, which of the following would have to be the case?改善题（做法：找老观点的缺点——打倒老观点的两个理由，取非；说明两个原因不成立）
I. All neurotransmitters would increase the short-term concentration of cyclic AMP in target neurons.
II. Substances other than caffeine that inhibit the production of phosphodiesterase would be stimulants.理由二
III. All concentration levels of caffeine that are high enough to produce stimulation would also inhibit the production of phosphodiesterase.理由一
(A) I only
(B) I and II only
(C) I and III only
(D) II and III only（D）
(E) I, II, and III
6. According to Snyder et al, all of the following compounds can bind to specific receptors（两类：AD，咖啡因的相似物质） in the brain EXCEPT
(A) IBMX
(B) caffeine
(C) adenosine
(D) theophylline（E）
(E) phosphodiesterase
7. Snyder et al suggest that caffeine’s ability to bind to A1 and A2 receptors*7 can be at least partially attributed to（因果） which of the following?直接事实题
(A) The chemical relationship between caffeine and phosphodiesterase
(B) The structural relationship*7B between caffeine and adenosine
(C) The structural similarity between caffeine and neurotransmitters
(D) The ability of caffeine to stimulate behavior（B）
(E) The natural occurrence of caffeine and adenosine in the brain
8. The author quotes Snyder et al in lines 38-43 most probably in order to举例作用题（服务于第三段——提供论据支持新观点）
(A) reveal some of the assumptions underlying their theory
(B) summarize*8B a major finding of their experiments
(C) point out that their experiments were limited to the mouse
(D) indicate that their experiments resulted only in general correlations（B）
(E) refute the objections made by supporters of the older theory
9. The last paragraph of the passage performs which of the following functions?
(A) Describes a disconfirming*9A experimental result and reports the explanation*9A given by Snyder et al in an attempt to reconcile this result with their theory.例外的情况及解释
(B) Specifies the basis for the correlation observed by Snyder et al and presents an explanation in an attempt to make the correlation consistent with the operation of psychoactive drugs other than caffeine.
(C) Elaborates the description of the correlation observed by Snyder et al and suggests an additional explanation in an attempt to make the correlation consistent with the older theory.
(D) Reports inconsistent experimental data and describes the method Snyder et al will use to reanalyze this data.（A）
(E) Provides an example of the hypothesis proposed by Snyder et al and relates this example to caffeine’s properties.
责任编辑：sealion1986
