Heptad
n. 七个, 成七的一组, 七价原子\\n[化] 七价物; 七价的
🗣️ 情景例句
I've been thinking about it for weeks now.
为这事我想了几个星期。
Civility costs nothing.
礼貌不须什么代价。
Man-made satellites have been sent up into space by many countries.
许多国家都成功地把人造卫星送入了太空。