As a very general rule, think of a "comma -ing" as modifying the clause that it's touching (but the "comma -ing" could come at the beginning, middle, or end). When it comes at the beginning, we often think of it as a noun modifier, but it's still the same thing. Slipping on the ice, I fell and broke my ankle. (Ouch!) --> I'm not just trying to say that *I* slipped on the ice. I'm trying to say that, as a result of slipping on the ice, *I fell.* I slipped on the ice, breaking my ankle. --> again, it's not just that I broke my ankle - it's that I broke it because I slipped. Note that I wouldn't say: I fell and broke my ankle, slipping on the ice. Why not? --> In general, there's a sequence to these constructions. The thing that's written first happens first, and the second thing happens after, as a result of, as a consequence of the first thing.
再来是OG12 #30的例子: 我的excel上当时就摘抄了一个instructor的解释: Try to read the sentence aloud with “protecting” and see if it makes sense:
…, animal-hide shields with wooden frames were essential items of military equipment, protecting warriors against enemy arrows and spears.
Not sure if it sounds right? Try flipping the two phrases(这个可行么?????) around like we did earlier by putting the descriptive phrase first and see if that makes sense:
Protecting warriors against enemy arrows and spears, animal-hide shields with wooden frames were essential items of military equipment.
但这样不会改变句子的意思么?一个是作为adverbial modifier一个是作为 noun或者verb modifier 看看OG12 30题 For members of the seventeenth-century Ashanti nation in Africa, animal-hide shields with wooden frames were essential items of military equipment, a method to protect warriors against enemy arrows and spears. (A) a method to protect (B) as a method protecting (C) protecting (D) as a protection of (E) to protect
放在句末protecting表示的是一个结果(essential-----导致了protecting) 如果protecting放在句首就是(because of protecting-----were essential,就像baby姐之前给出的stacey的例子一样)