gmatdriller wrote:Sleeping pills had been showing up with regularity as a factor in traffic arrests, sometimes involving drivers who later claim that they have no memory of getting behind the wheel after ingesting the pills.

A...
B: had been showing up with regularity as factors in traffic arrests
C: have been showing up with regularity as a factor in traffic arrests
D: have been showing up with regularity as factors in traffic arrests
E: have been showing up with regularity in traffic arrests

Source: Manhattan CAT Test1; OA C

How do we figure out the subject in this case--

X's had/have been showing up with Y
(i) "as factors" or
(ii) "as a factor"

Thanks to help explain

First, I don't find this sentence to be very tight. The structure is awkward the ideas are not that well expressed.

Still, here is the rationale behind the official answer.

First let's choose between had and have.

In looking at the second half of the sentence, we see drivers who later claim. The verb claim is in the present tense, implying that the events are still happening. So to match with this we need the past perfect have. If the modifier instead included the wording involving drivers who later claimed, then had been could make sense in the underlined portion.

As far as a factor versus factors goes, while I am not a fan of the wording either way, the rationale behind the official answer is that sleeping pills were just one factor contributing to the situation. So factor should be singular. If you ask me it's a little sketchy. For one thing, one could make the case that each pill was a factor and that one could say, "The pills were factors." Myself, I would prefer something like, The use of sleeping pills has been showing up with regularity as a factor.

Maybe someone else will have a different take on this, but that's how I see it.

I feel the original sentence is correctly transcribed as below:

Sleeping pills have been showing up REGULARLY as a factor in traffic arrests sometimes involving drivers who later claim that they have no memory of getting behind the wheel after ingesting the pills.

In which case

"with regularity as a factor" = "regularly as a factor"

What do you think?

gmatdriller wrote:I feel the original sentence is correctly transcribed as below:

Sleeping pills have been showing up REGULARLY as a factor in traffic arrests sometimes involving drivers who later claim that they have no memory of getting behind the wheel after ingesting the pills.

In which case

"with regularity as a factor" = "regularly as a factor"

What do you think?

I like it better as you have written it, using regularly instead of with regularity.

Ideally the whole thing could be rejiggered to something along the lines of The use of sleeping pills has shown up regularly as a factor in traffic arrests, some of which involve drivers who later claim that they have no memory of getting behind the wheel after ingesting the pills.

Now that would definitely be the OA.

Sleeping pills have been showing up with regularity as a factor in traffic arrests, sometimes involving drivers who later claim that they have no memory of getting behind the wheel after ingesting the pills.

Generally, a COMMA + VERBing modifier serves to express an action attributable to the PRECEDING SUBJECT.
Here, involving seems to refer to sleeping pills (the preceding subject), implying that the SLEEPING PILLS are responsible for INVOLVING drivers.
Not the intended meaning.
I would ignore this SC.