______a written permission, he had to write another letter to the president of the university.
A.Not giving
B.Not having been given
C.Having not given
D.Having not been given
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B解析试题分析：考查非谓语动词作状语。句意：因为没有给他一个书面的批准，他不得不另外写了一封信给大学校长。根据非谓语动词的否定，not应该置于非谓语之前，排除C和D，然后根据句意，give与he之间的关系为被动，确定