帮忙吧！！

　the production of cosmetics, once of limited economic importance, has developed into a mulitibillion-dollar industry in (their )twentieth century.

D显然错误．

谁能帮解释下once of limited economic importance这句话的语法关系吗？？？

personal opinions:

"once' is an adverb in this sentence.   the whole sentence should be:

the production of cosmetics, (which were) once of limited economic importance, has developed into a mulitibillion-dollar industry in (the )twentieth century.

of limited economic importance/n  = xxxx  important/adj.

of limited economic 　　关键是它为什么这样写？？　　帮忙解释清楚点好吗？本人不胜感激！！！

of + importance/n = important/adj.

it is so hard to convert "of limited economic importance" into its form of adjectives.

"limited economic important", which is obviously wrong. there is no adverb form of "economic";   it's so hard to write "xxxx important" correctly.   that is how come they write "of limited economic importance"

personal opinion

if not()irregular eastern boundary,Pennsylvania would be almost rectangular in shape.

A.the   B.that the   C.it has   D.for its

选什么？为什么？　　能解释清楚点好吗？

i would choose A.  the whole sentence would be:

if (there were) not the irregular eastern boundary, PA would be almost rectangular in shape.

虚拟语气.　thus, C is wrong.    B and D are obviously wrong  because those are even not the whole sentences.

谢谢