核心问题
Essential English 中有这样一个句子：
Terrible weather we are having, isn't it? (Book 3, L4, p. 28) 我们的英语教师在解释这个句子时说: 句中的附加疑问句是一种不规则用法: 因为附加疑问句的主语 (it) 跟句子的主语 we 不一致。
词典解答
上面句子里的附加疑问句并非是不规则用法,而是规则用法,因为 Terrible weather we are having 系 It is terrible weather (that) we are having 的省略形式。很多人之所以把 isn't it 解释为不规则用法,是因为他们把 Terrible weather we are having 看成是 We are having terrible