The probability of failure for a project element is often called exposure to risk，or risk exposure．This exposure may be mitigated by taking measure to avoid a particular approach or use of specific technologies．When the risk exposure cannot be reduced through selection of another alternative，the project manager should______．

A．conduct further studies and analysis until a more attractive alternative is found

B．disregard the exposure to risk because nothing can be done

C．not performs the activities with risk exposure and save the money which would have been spent on them

D．establish a contingency plan to overcome any adverse activitwhich may include a contingency allowance

改善混凝土（）的外加剂，如膨胀剂、碱骨料反应仰制剂。