表主动时 ,用现在分词.表被动时,用过去分词.如：
Weather permitting,they will go on an outing to the beach tomorrow．＝If weather permits,they will go on an outing to the beach tomorrow．（如果天气允许的话,他们将在明天组织一次海滨小游.
My shoes removed,I entered a low-ceilinged room,treading cautiously on the soft tatami matting．＝After my shoes were removed, I entered a low-ceilinged room,treading cautiously on the soft tatami matting．（我脱掉鞋子后,走进一间屋顶很低的房间,小心翼翼地踩在柔软的塌塌米垫子上.）
再问： Weather permitting为啥用主动
再答： 完整句子就是
If the weather permits
没有使用被动语态，故事主动的。
再问： 我不会把句子变完整
再答： 这需根据语境，确定是表示何种状语，然后再变成相应的完整句子。
