请教OG10-233

233. Recently implemented "shift-work equations" based on studies of the human sleep cycle have reduced sickness, sleeping on the job, fatigue among shift workers, and have raised production efficiency in various industries.

(A)
                    fatigue among shift workers, and have raised

(B)
                    fatigue among shift workers, and raised

(C)
                    and fatigue among shift workers while raising

(D)
                    lowered fatigue among shift workers, and raised

(E)
                    and fatigue among shift workers was lowered while raising

答案是C, 我知道sickness, sleeping on the job和fatigue among shift workers 三个名次

（名词性短语）并列做reduce的宾语；但后面的while raising是什么成份呢？其逻辑主语是什么呢？

谢谢！