positive clause 就是 affirmative clause 的意思——表示“肯定分句”“肯定从句”，与 negative clause（否定分句，否定句从句）形成对比。如：
Like positive
clauses, however, they may be followed by positive tag clauses that do not have
subject-operator inversion.
句子大意：然而，和肯定分句一样，它们（应该是指否定分句）后面可以跟主语与功能词不倒装的肯定附加分句。
