A mysterious illness, referred to as “ a typical phenomena”, has been brought under control, the government said on Wednesday, ______ no cause of it has been made public.

A．though

B．when

C．that

D．because

联合国第三任秘书长是（）。

A.瓦尔德海姆

B.约翰逊

C.拉吉夫

D.吴丹