问题详情

The authors discussion of the "mechanism that provides blood tryptophan to the brain cells"(lines 44-45)is meant to
A．stimulate further research studies.
B．summarize an area of scientific investigation.
C．help explain why a particular research finding was obtained.
D．provide supporting evidence for a controversial scientific theory.
E．refute the conclusions of a previously mentioned research study.请帮忙给出正确答案和分析，谢谢！