gmatdriller wrote:Pls explain distinction btw "had" vs "have" with the timeline concept.

The answer choices in this question include a distinction involving one possible have construction.

Have can be used, among other things, to create a construction that conveys that something is ongoing. So, for instance, one might say, "Astronomers have been studying the nearby planets and in the process they have so far discovered 17 that are orbited by planets the size of Jupiter."

So that studying and discovering process is ongoing and so the use of have makes sense there.

In the example you gave, the work being discussed is only that which went on through 1999, a date in the past. So the work being discussed is not ongoing work. It's work that was completed by 1999. So using have would not make sense and had is better there. The sentence is not saying that they have been discovering; it's saying that by 1999 they had discovered 17 planets.

Now to be clear, there are other ways that have can be used to make verb constructions. There are times when have is used even when something is not ongoing. For example, John and Sue have succeeded in their quest to find the holy grail. is an ok sentence. Are they succeeding on an ongoing basis? Not really. So you can't just mechanically ask whether something is ongoing and expect to always get a right answer. You need to look at the context and at the meaning created by answer choices to determine what construction is best.

Anyway, ongoing versus not ongoing is the distinction here.

Thanks Murrah for the explanations.

In a sense the "17 stars that ARE orbited" are still orbited by planets at the time of writing?
If that is the case, then, the 2 actions(discovery & orbiting) are not both past events.

I expect discovery happened 1st in the past, THEN "orbited" happened more recently.
The use of "are" but not "were" suggests that the orbiting is still happening.

HAD DISCOVERED ARE ORBITTED
PAST PERFECT SIMPLE PAST TILL PRESENT


Is this correct?

gmatdriller wrote:Thanks Murrah for the explanations.

In a sense the "17 stars that ARE orbited" are still orbited by planets at the time of writing?
If that is the case, then, the 2 actions(discovery & orbiting) are not both past events.

I expect discovery happened 1st in the past, THEN "orbited" happened more recently.
The use of "are" but not "were" suggests that the orbiting is still happening.

HAD DISCOVERED ARE ORBITED
PAST PERFECT SIMPLE PAST TILL PRESENT


Is this correct?

Yes, exactly. The orbiting is still happening.

Not sure you need to say simple past through present, maybe just past through present.

Agreed, it should be past into the present.

Thanks