以下为句子列表：
英文: So far, a male contraceptive pill has proved difficult to produce because of a basic biological fact of human reproduction: a man naturally produces about 150 million sperm each day of his adult life.
中文: 人类繁殖有一个基本的生理现象，一个成年男性每天能产生1亿5千万个精子，所以迄今，人们很难生产出男性避孕药。
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