1 （）,it immediately ran away.a.Observing her b.On being oberved c.Having been oberved d.On her being oberverd2 The experts were now fully convinced that the animal ( ) a puma.a.must be b.should have been c.can only be d.could only have been
问题描述：
1 （）,it immediately ran away.
a.Observing her b.On being oberved c.Having been oberved d.On her being oberverd
2 The experts were now fully convinced that the animal ( ) a puma.
a.must be b.should have been c.can only be d.could only have been
答
c和a
答
第一题选D，on one’s being done表示一。。。就。。。
第二题选A，这里的must表猜测
答
1.b ，一…就 2 a,从concince可看出专家很确定，所以选第一个
答
每一个选D,
第二个选A.
答
1 b 2 a
答
1.D On being observed ，一被人看到 on 是介词“一……就……”
“一被看到，它立即就逃跑了”
2.A must 表示非常肯定的推测 “一定是”
“专家们现在充分确信那只动物一定是美洲豹”
答
1.B On ...和 when ...,意思都一样,“当……的时候”.On being observed也可以写作On the time when it is being observed 句意：一被人看到,美洲狮就跑掉了.2.D 情态动词表达推测的语意概念时,对于过去事实推测一定...
答
1 D2.A