Singular-plural alternation. Having said that, I believe it truly is the same variety of phenomenon. Semantics is stepping in and influencing the verb arrangement — it isn't really always a purely syntactical decision. 知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 The subject on the sentence "Is either of you free?" is "possibly" not "you" https://sexcamgirls.live/