2003年10月16日，我国自行研制的“神舟”五号载人飞船顺利发射和返回．运送飞船的长征二号F型运载火箭所使用的燃料是偏二甲肼（化学式是C₂H₈N₂）．偏二甲肼相对分子质量是  　_________，各元素的质量比是___________．

In requirements engineering, requirements elicitation is the practice of collecting the requirements of a system from users, customers and other stakeholders. In the following practices, ( ) is rarely used in requirements elicitation.

A. brain storming

B. interview

C. questionnaire

D. Monte Carlo analysis