1、These levels of natural and background radiation is normal.
但這些都只是正常輻射。

2、But natural background radiation is more than 100, 000 times the highest levels detected.
但其檢測量大大高于自然本底輻射量一萬倍。

3、But natural background radiation is more than 100,000 times the highest levels detected.
但其檢測量大大高于自然本底輻射量一萬倍。

4、Cosmic X-Ray Background Radiation and Active Galactic Nuclei
宇宙X射線背景輻射與活動星系核

background radiation翻譯