Oetzi, the 5, 000 year old "Iceman", ________ on the border between Italy and Australia in 1992.[ ]

A. was discovering      

B. was discovered    

C. had been discovered    

D. discovered

健康人定期牙周洁治间隔的时间以下哪项是恰当的（）。

A.3个月

B.2个月

C.6～12个月

D.1个月

E.2年以上