You can only be sure of _____ you have at present; you cannot be sure of something _____ you might get in the future.

A．that; what 　

B．what; 不填

C．which; that

D．what; which

为明确诊断GH缺乏性侏儒症，需做的兴奋试验有（）

A.胰岛素低血糖兴奋试验

B.精氨酸兴奋试验

C.左旋多巴兴奋试验

D.可乐定兴奋试验

E.GHRH兴奋试验