In the past 50 years, under the leadership of the CPC, the situation of Tibet has___________much better than it used to. 

A．turned to

B．turned off

C．turned out

D．turned into

生产经营单位的安全生产管理机构以及安全生产管理人员可以委托中介机构落实单位重大危险源的安全管理措施。