Quadrivalence
n. 四价\\n[医] 四价
🗣️ 情景例句
They are eager to learn English.
他们急着要学英语。
This problem is hard to solve.
要解决这个问题不简单。
as the wave leaves the particles behind back to its starting point again.
当波浪把微粒留在身后时又回到出发点。