Quadrivalency
n. 四价
🗣️ 情景例句
Neither.
都不是。
While there is life, there is hope.
留着青山在，不怕没柴烧。
Many firms, for instance, have great difficulty in obtaining technical or scientific books from libraries
比如，很多公司向图书馆借阅科技书籍时感到很困难，