⑦It must have been an instinctive reaction but it saved my life.
⑧The boy pretended to have known it.
1.以上句子分别使用了不同的________或________形式 来表达“完成”的概念。
2.根据以上例句,表示“完成”动作的形式有: ________时态(句①), ______时态(句②和句③),过去完成进行 时态(句⑥), ______时态(句④), ______的完成式(句⑧),动词ing形式的完成式(句⑤),含有情态动词的完成时态(句⑦)。
灵长类动物的成功克隆获得了全世界的赞誉,被认为是一 项巨大的突破,从而为治愈多种疾病、延缓衰老提供线索。
【答案】3.led to; how to prevent
4.For years, there had been ________ animals artificially. 多年来,人们一直在尝试人工克隆动物。 5.At first, Dolly grew normally, but later she ________ that is more normally found in much older animals. 起初,多莉发育正常,但后来患上了一种疾病,这种疾病 更常见于衰老的动物。 【答案】4.attempts to clone 5.developed an illness
things and discover the differences between them.
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5.If you say that something will happen or continue forever,