Here, what we mainly need to choose is the had/have and the less/fewer than part.

Coming to the original sentence, the sentence starts off with "Since 1966,..." this implies that it is an ongoing activity from 1966 to present. So, here we need to choose have and not had. Had implies only past tense whereas have suggests that from past to current, so we choose have.

So, A and D are eliminated.

Now, come to less than fewer than.

Fewer than is used for countable nouns which have plurals such as dogs, newspapers, umbrellas, men,etc. For example, there are fewer boys present today, than there were yesterday.

Less is used for uncountable nouns or does not have a plural such time, rain, money, Air, water etc.

Example: I have less money now than I had a month back.

Less is also used when a Number is on its own and associated with its unit of measurement.

Example: Thier marriage lasted less than two years.

Now one thing to note here is that "I have fewer than two dollars" is not correct but "I have less than two dollars" is correct, as dollars is the unit of measurement and two is the quantity.

Using this logic, in the above sentence, less than three years is the correct version.

So, the correct choice is B!

thank u...it was a good explanation...

basically when comparison between quantities involving units is involved less than is used even if it is a countable noun

nafiul9090 wrote:Since 1966, roughly 21 percent of those enlisted in the USMC had reached
an E-5 ranking in fewer than three years.

(A) had reached an E-5 ranking in fewer than three years
(B) have reached an E-5 ranking in less than three years
(C) have reached an E-5 ranking in under three years
(D) had reached an E-5 ranking in less than three years
(E) have reached an E-5 ranking in fewer than three years

guys any thought ??

since points that have is needed not had so B,C,E remain...out of these I will choose B....not sure why ?

As per me, correct answer is E.
Not sure why Birottam beleives that less should be used instead of fewer.
Here three years is surely a countable entity and thus the use of fewer is justified.
In case of dollars, we say I have less than 3 dollars because saying
I have fewer than 3 dollars would indicate saying that I have literally fewer that 3, 1 dollar bills.
But here fewer than 3 years seems correct.

nafiul9090 wrote:Since 1966, roughly 21 percent of those enlisted in the USMC had reached
an E-5 ranking in fewer than three years.

(A) had reached an E-5 ranking in fewer than three years
(B) have reached an E-5 ranking in less than three years
(C) have reached an E-5 ranking in under three years
(D) had reached an E-5 ranking in less than three years
(E) have reached an E-5 ranking in fewer than three years

guys any thought ??

less : it can act as an adjective ( noun modifier), adverb( verb modifier ) and as a noun
lower/fewer : always act as an adjective

"in" being a preposition is always followed by a noun - Only B and D stands out.

Since X,....- present perfect tense should be used and not past perfect. "Since 1966" is an adverb of time for an events started in the past and still continuing.

Hope this helps !!

Birottam Dutta!!! what he said is absolutely correct. The reason is that in choosing between the
countable and uncountable nouns, there are 4 exceptions, namely:
1. Time 2. Distance 3. Speed and 4. amount or money

This thing actually is given in the spidey's notes and the sahil's notes.

Kindly refer to them.

By the way thanks Birottam...

Thanks for the reply.
Yes, there is more to it.
We use less/more with following countable quantities.
1.Time 2.Money and 3.Distance.
Confirmed here by Knewton https://www.beatthegmat.com/an-odd-st-t70077.html

I do not think there is any point in looking at the countable and uncountable quantities here. This difference comes only when "less" and "fewer" both acts as an adjective.

Here, "less" is clearly taking the noun slot - the object of the preposition and so "fewer" cant be used.

Considering some good example stated above :

I have less money now than I had a month back. - since "less" is an adjective. here the concept of countable and uncountable will come.

But, in this example

Their marriage lasted less than two years.

here "less than two year" is an adverb of time and hence "less" should be used and not "fewer".


Hope this helps !!