八．句型转换. (每小题2分, 共10分)
81. It is obvious that he has known the truth.
_____________, he has known the truth..
82. I happened to meet an old friend in the street yesterday.
I met an old friend _____________ ____________ in the street yesterday. 
83. The problem needs discussing.
The problem needs __________ __________ ____________.
84. The government gave an order. All the victims in the earthquake of Yushu County, Qinghai Province were rescued.
The government gave an order _________________________________________________.
85. To master a foreign language is not an easy job.
_______ _______ not an easy job ___________ _________ a foreign language.