common knowledge 常识，大家都知道的事。为避免头重脚轻，真正的主语 that the moon itself does not give off light（月球本身不发光）放到了句子的后面，主语由it来代替，整句话译为：月球本身不发光，这是常识。
______is common knowledge that the moon itself does not give off light.
common knowledge 常识，大家都知道的事。为避免头重脚轻，真正的主语 that the moon itself does not give off light（月球本身不发光）放到了句子的后面，主语由it来代替，整句话译为：月球本身不发光，这是常识。
