U2, I agree, "been" stands a bit alone and I had to convince myself to bind it to "they have (...).

But I prefered E to D coz I dont like "prescribed too low a dosage". It doesnt sound right. I wd prefer "prescribed a too low dosage".

Answers are D and C...sure

as described ---

1st one
A - having, for example been prescribed a drug as a dosage too low to be effective or having been ---> wrong awkward use of for example.
B -- having, for example, a drug prescription that was ineffective because the dosage was too low, or being ----> wrong awkward.
C -- as, for example, having too low of a dosage of prescribed drug for it to be effective, or being ----> wrong usage of as and not parallel.
D -- when they have, for example, been prescribed too low a drug dosage for it to be effective, or were ---> correct
E -- for example, when they have a drug prescription with a dosage too low to be effective, or been --->awkward

2). Officials at the United States Mint believe that the Sacagawea dollar coin will be used more as a substitute for four quarters rather than for the dollar bill because its weight, only 8.1 grams, is far less than four quarters, which weigh 5.67 grams each.

A -- more as a substitute for four quarters rather than for the dollar bill because its weight, only 8.1 grams, is far less than ---> wrong for more as ... rather than
B -- more as a substitute for four quarters than the dollar bill because it weighs only 8.1 grams, far lighter than ---> wrong comparison
C -- as a substitute for four quarters more than for a dollar bill because it weighs only 8.1 grams, far less than ----> correct comparison
D -- as a substitute for four quarters more than the dollar bill because its weight of only 8.1 grams is far lighter than it is for -----> wrong comparison
E -- as a substitute more for four quarters rather than for the dollar bill because its weight, only 8.1 grams, is far less than it is for ----> wordy, usage of more ... rather than is not common

2nd question

Officials at the United States Mint believe that the Sacagawea dollar coin will be used more as a substitute for four quarters rather than for the dollar bill because its weight, only 8.1 grams, is far less than four quarters, which weigh 5.67 grams each.

A -- more as a substitute for four quarters rather than for the dollar bill because its weight, only 8.1 grams, is far less than

B -- more as a substitute for four quarters than the dollar bill because it weighs only 8.1 grams, far lighter than four quarters

C -- as a substitute for four quarters more than for a dollar bill because it weighs only 8.1 grams, far less than

D -- as a substitute for four quarters more than the dollar bill because its weight of only 8.1 grams is far lighter than it is for

E -- as a substitute more for four quarters rather than for the dollar bill because its weight, only 8.1 grams, is far less than it is for

as you can see ||sm is interrupted in A D and E

B has a WRONG comparison... as a substitute vs. four quarters.... definitely wrong

The more I read the sentence, the more I think you might be right.
What convinces me is that the past tense of D fit more to the past tense of the main sentence. That's not the case with E.

And I m thinking also if I am not wrong with (2)...

1. D (remember it from Kaplan 800)
2. C (former error log entry)

I rejected A because of lack of comma after "for example". Is this a typo???
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

This is not a tense. This is an absoulte phrase. usage of "Having been" is not a problem. See this:

http://www.bartleby.com/64/C001/047.html

For absolute constructions see this:
http://www.bartleby.com/64/C001/001.html

But I am still confused by the no use of comma.
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

1). Some patients who do not respond therapies of depression may simply have received inadequate treatment, having, for example been prescribed a drug as a dosage too low to be effective or having been taken off a drug too soon.

A -- having, for example been prescribed a drug as a dosage too low to be effective or having been

having, for example been prescribed ......or having been taken off

is parallel. That's why i liked this one. I realized for example lacks a comma but I remember reading in one of the test prep books that GMAT normally does NOT test punctuation errors. So long as the there are no Grammatical structure errors, it should be fine though I may stand corrected if I have misinterpreted this clause.

B -- having, for example, a drug prescription that was ineffective because the dosage was too low, or being

Clearly wrong. A drug prescription can't be ineffective.

C -- as, for example, having too low of a dosage of prescribed drug for it to be effective, or being

as, for example, having too low of a dosage ... or being is not parallel

D -- when they have, for example, been prescribed too low a drug dosage for it to be effective, or were

when they have been prescribe and or were ..tense conflict and unparallel structure.

E -- for example, when they have a drug prescription with a dosage too low to be effective, or been

Again unparallel structure is basically why i ruled this one out.

Dahiya you are right there is a comma after "for example" -- I am extremely sorry for the typing mistake, Am sorry once again for messing up the whole SC discussion.

Also in the 1st, (A) does not have the ambiguity w.r.t "they" which is present in D and E.

"They" could refer to "therapies of depression" or "patients".