isotope|isotopes

医生使用放射性同位素来追踪肿瘤位置。

Doctors use a radioactive ___isotope to locate the tumor.

氢有三种同位素：氕、氘和氚。

Hydrogen has three ___isotopes: protium, deuterium, and tritium.

氢元素的同位素氘常用于核反应堆。

Deuterium, an ___isotope of hydrogen, is commonly used in nuclear reactors.