zhongshanlh Wrote:however, in this problem, i don't totally understand what is the function of as in the sentence"as seen in the rings visible in the cross sections of their trunks"
so please clarify me.
as usual, i have no idea what you would call this in terms of grammar terminology. but, basically, the meaning here is that you can see
evidence of the thing, but not the thing itself. i.e., in this case, you obviously can't literally
see a rate by looking at tree rings, but you can see stuff from which the rate can be determined, or, in other words, stuff that's
related to the rate.
here's another example:
the reaction will produce brown smoke, as described in the laboratory manual.
this means that the lab manual says "hey, there's gonna be smoke" -- i.e., the lab manual talks [i]about the smoke -- but doesn't describe the smoke itself.
if the lab manual actually gives a physical description of the smoke, then you can write "...the smoke described in the lab manual".
sorry i can't help you with grammar terms, but i pretty much don't know any of those unless i can google them, and this isn't really something that is google-able.
in this kind of construction--->COMMA +verbED
i remember that the verbED should always be regarded as a past participle and used to modify the noun that close to it in the previous clause(so it is always a noun modifier)
yes on the noun modifier part; no on the "closest noun" part.
if you have a comma in front of that participle, then it will usually modify the subject of the clause, not the closest noun.
for instance:
*
Tanya collapsed onto the couch, exhausted from a 14-hour work shift (here, "exhausted" modifies the subject "Tanya")
if you want to modify the closest noun, then you are normally going to ditch the comma:
[i]in the attic, i found an old box inlaid with precious stones.[/]
(here, "inlaid" modifies "box")
