Empress Wu a. achieved nothing positive during her rule. b. made a significant contribution to the civil service examination system. c. was assassinated on her fortieth birthday. d. found a rationalization for her rule in a Daoist sutra. e. deposed her courtiers at the age of 80 and went on to rule another eight years.

B:made a significant contribution to the civil service examination system.

Explanation:

Empress Wu was the only female emperor in the history of China. She reigned during the Tang Dynasty killed her children in order to become China's Only Female Ruler,  she helped to improve the lives of the peasants by lowering taxes, building new public works, improving farming techniques and contribution to the civil service examination system(Chinese imperial examinations).

b. made a significant contribution to the civil service examination system

Explanation:

During the first half of the Tang dynasty’s rule, a civil service system was established. In it, scholar-officials were selected through standardized tests and previous references.

Eventually, Empress Wu changed the imperial examinations system so a new group of elite officials arising from more modest backgrounds could be included.

the correct answer is d