1994年，国家财政体制开始（）改革。 A.包干制 B.单元财政 C.分税制 D.自

动态规划是解决（）最优化问题的一种理论和方法。

— John seems happy, even though his wife left him and he lost his job.

— I think he __________ to put on a brave face.

A．will try

B．has tried

C．had tried

D．is trying

在生产和运输过程中设备和管线的泄漏是石化行业污染的途径之一。

《报检员资格证》由( )统一印制。

A．当地检验检疫机构
B．国家质检总局
C．省级以上检验检疫机构
D．县级以上检验检疫机构

偏头痛在（）岁是高发期

A.30

B.40

C.50

D.60