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
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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
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
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
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要用于情态动词have以及过去分词形式进行搭配.A 项 must be 是对客观现实的一种推测,应该跟主句的谓语动词“were now fully convinced ”保持一致,C项的can 与前面 的时态不一致,需改为could；B项should have been 表示本该是,而实际上不是的意思.因此答案为D.
每一个选D,
第二个选A.
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”
1 D2.A
1.b ，一…就 2 a,从concince可看出专家很确定，所以选第一个
1 b 2 a
c和a
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