OG rc84

tulip37

84. According to the passage, when the authors began
their first studies, they were aware that
(A) they would eventually need to design
experiments that involved feeding rats high
concentrations of protein
(B) tryptophan levels in the blood were difficult to
monitor with accuracy
(C) serotonin levels increased after rats were fed
meals rich in tryptophan
(D) there were many neurotransmitters whose
production was dependent on metabolic
processes elsewhere in the body
(E) serotonin levels increased after rats were
injected with a large amount of tryptophan


OG后面的解释是，选E
Th e
investigators wanted to see if an increase in
serotonin levels would be observed after rats ate
meals that changed tryptophan levels in the blood.
Earlier research had already established that
injecting tryptophan increased serotonin levels.



可是文章中没有说Earlier research had already established that  injecting tryptophan increased serotonin levels.啊。而且题目是问when the authors began their first studies，而E选项是这个first study的结论，当他们开始这个study的时候应该还不知道这个结论啊。求赐教@！thx~

kronorrt

原文line 9：Our first studies sought to determine whether the increase in serotonin observed in rats given a large injection of the amino acid tryptophan might also occur after rats ate meals that change tryptophan levels in the blood.

答案就在这句话里，句子主干是 studies sought to determine whether the increase might also occur.    而observed in rats given a large injection of the amino acid tryptophan 是对increase的修饰。意思是 serotonin增加，曾经在被大量注射tryptophan的小白鼠身上观察到，这种增加会不会再次（also!!）发生，当小老鼠吃了改变tryptophan的食物之后