Hi quetz!

Let's see if I can help (or at least point you to some great help).

quetz wrote:1) When "None of the" is followed by a plural noun, what is it? singular or plural? Manhattan Gmat SC guide says it can be singular or plural (but plural according to their SANAM prounouns principle), but Kaplan 800 says its singular; period.

My fellow Manhattan GMAT instructor (Ron "the literary genius" Purewal) explained the total LACK of importance of this issue in the following post:

https://www.beatthegmat.com/sanam-pronouns-t17033.html [Scroll to the bottom of that thread to see his fantastic reply!]

quetz wrote:2) Must one use past perfect (instead of simple past) in situations in which the sequence of events are logically clear?
Manhattan Gmat prep SC guide says we should use past perfect only to clarify or emphasize the sequence of events. Any rule of thumb here?

As for this issue, we don't HAVE to use past perfect to set up a past sequence of events, but we can't just use logic, we MUST have some other time/sequence cue makes the order of events certain. Lets look at a couple of examples:

OG Verbal #37 wrote: Some buildings that were destroyed and heavily damaged in the earthquake last year were constructed in violation of the city's building code.

• (A) Some buildings that were destroyed and heavily damaged in the earthquake last year were
  (B) Some buildings that were destroyed or heavily damaged in the earthquake last year had been
  (C) Some buildings that the earthquake destroyed and heavily damaged last year have been
  (D) Last year the earthquake destroyed or heavily damaged some buildings that have been
  (E) Last year some of the buildings that were destroyed or heavily damaged in the earthquake had been

OA B

Sure, logically it might be clear that the buildings had to be constructed BEFORE they were damaged or destroyed, but in the original sentence there is no GRAMMATICAL/STRUCTURAL way to prove it (each only has the simple past and there are no dates comparing the 2, so it isn't clear).

Therefore, we have to find an answer that sets up the clear order of events: the destruction happened in the past (simple past) but the construction happened even earlier (past perfect) = choices B and E. We then eliminate E because of the location of the modifier "last year" - but that is a discussion for another thread!

But now, we need an example that doesn't need past perfect to show the sequence of events because there IS a grammatical or structural sequence...

OG12th #90 wrote:Although early soap operas were first aired on evening radio in the 1920's, they had moved to the daytime hours of the 1930's when the evening schedule became crowded with comedians and variety shows.

• (A) were first aired on evening radio in the 1920's, they had moved to the daytime hours of the 1930's
  (B) were first aired on evening radio in the 1920's, they were moved to the daytime hours in the 1930's
  (C) were aired first on evening radio in the 1920's, moving to the daytime hours in the 1930's
  (D) were aired first in the evening on 1920's radio, they moved to the daytime hours of the 1930's
  (E) aired on evening radio first in the 1920's, they were moved to the 1930's in the daytime hours

OA is B

In this case, the right answer used only simple (passive) past tenses for "were aired" and " were moved" because the dates (1920s and 1930s) were doing the job of establishing the chronology (aired in 1920s, then they were moved in the 1930s).

So let's sum this up. If I want to talk about events that happened in the past and I'm not trying to establish order (they happened at the same time for example), I use simple past. If I need 2 events to happen in the past in a specific order, I either need to use a combination of simple and perfect past, OR I can throw dates/times/time markers in the mix and go simple.

Maria had finished her dinner when the rest of the group arrived. ("had" says that the finishing of dinner happened BEFORE the rest of the group arrived)

Maria finished her dinner when the rest of the group arrived. (all simple past makes it sound as if the finishing and arriving happened at the same time - ie. when they got there she finished it, the time sequence is NOT the same)

Maria finished her dinner before the rest of the group arrived. (adding the "before" now makes it clear using only simple past that the finishing happened before the group arrived)

Hope this clears it up!

Whit