Today’’s lecture we’’ll center on the prehistoric people of Nevada Desert. Now most of these prehistoric desert people (36)______the countryside throughout the year. You might think that they’’re wandering aimlessly. Far from it, they actually followed the (37)______of carefully planned moves. Where they moved depended on where food was (38)______. Places where plants were ripening or fish were (39)______. Now often when these people moved, they carried all their (40)______on their backs. But if the journey was long, extra food and tools were sometimes stored in caves or (41)______rocks. One of these caves is now an exciting (42)______ site. Beyond its small opening is a huge underground (43)______. Even though the cave is very large. It was certainly too dark and dusty for the travelers to (44)____________. But it was a great place to (45)____________. And tremendous amounts of food supplies and artifacts have been found there.The food includes dried fish, seeds and nuts. The artifacts include stone spear points and (46)____________. The spear points are actually rather small. Here is a picture of some that were found. You can see their size in relation to the hands holding them.

敏感性分析的一般步骤包括：①确定敏感性因素；②确定评价指标；③分析不确定性因素的波动幅度及其对评价指标可能带来的增减变化情况；④选择需要分析的不确定性因素。这些步骤的正确顺序应为（）。

A.①②③④

B.②④③①

C.②①④③

D.④③②①