下列核反应或核衰变方程中，符号X表示中子的是(  )

A：${}_4{}^9\text{B}\text{e}$ ＋ ${}_2{}^4\text{H}\text{e}$ → ${}_6{}^{12}\text{C}$ ＋X

B：${}_7{}^{14}\text{N}$ ＋ ${}_2{}^4\text{H}\text{e}$ → ${}_8{}^{17}\text{O}$ ＋X

C：${}_{80}{}^{204}\text{H}\text{g}$ ＋ ${}_0{}^1\text{n}$ → ${}_{78}{}^{202}\text{P}\text{t}$ ＋2 ${}_1{}^1\text{H}$ ＋X

D：${}_{92}{}^{239}\text{U}$ → ${}_{93}{}^{239}\text{N}\text{p}$ ＋X