问题
选择题
Land animals are believed ______ from sea animals.
A．to have developed
B．to have been developed
C．having developed
D．having been developed
答案
答案：A
考查非谓语动词。句意：陆地动物被认为是由海洋动物进化而来的。根据句意可知事情已经发生，故用不定式的完成时，选A。
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