有一读者问： 可否将 Having been shown the lab, we were taken to see the library. 改为 Shown the lab, we were taken to see library.?
现在分词完成被动式与及物动词的过去分词用作状语时，确有相同之处，如 Having been weakened by successive storms, the bridge was no longer safe 中 的 having been weakened 即可改为weakened 而意义不变。但有时二者并不完全等值，如 Having been asked to stay, I couldn't very well leave 中的 having been asked 则不完全等于 asked，因为 asked to stay 的意义不够明确，还可能有 when I was asked to stay 的含义。问题中 shown the lab 与 having been shown the lab 当然同义，但前者似乎给人一种急促之感，不及后者那样不紧不迫。顺便提一下，上述一类分词短语结构一般都用在书面语中，在口语中应教学生多用相应的从句结构。
