It is entirely reasonable for auditors (to believe that scientists (who know exactly where they are going and how they will get there )( who引导的定语从句修饰 scientists ) should not be distracted by( the necessity of keeping one eye on the cash register while the other eye is on the microscope.))(不定式做主语)
while the other eye is on the microscope 在介词 by 宾语里面做伴随状语
真个句子是IT 做形式主语的句子,也很常见.