Quadrivalency
n. 四价
🗣️ 情景例句
to meet the rest of the troop at two o'clock at the museum.
我们得在两点钟到博物馆与其他童子军会合。
Self-distrust is the cause of most of our failure.
我们的失败多数是由于缺乏自信。
and the railway of the future may well be the 'hovertrain',
未来的火车或许能成为气垫火车，