One of the four named is correct.

Not really all that implicit by that term. Now, had you said it was implicit by your mention of Green Arrow the one who got in, I probably wouldn't of said a thing. Tho, I only mentioned it because I have no clue about the answer and just have a need to bug you about something. And it's not easy to stay away from remarks about your old age and infirmity. :speechles

I also gave the comic title as Justice League of America. While there have been various and sundry "Justice League" books since then, I believe the only other one with that title just started a few years ago.

I really didn't think this was that difficult a question. The story to which I refer has been reprinted many times, including one very recent collection.

Well, I'll talk through my thinking.

EM, Atom and Hawkman were all around at this time.

I don't think Metamorpho was yet (although he was famously offered membership at some point and declined)

I guessed Atom and Hawkman (knowing they were the next two to join) but EM is a strong contender as Barry would have nominated him. So the "one right" makes me think it's him.

But then who's the other? I have no idea. The DCU was rather more sparsely populated back then.

Elongated Man and Captain Comet?

Nope, neither of those.

Here's a hint: another story was done a year later to explain how one of these heroes could have been nominated.

The Flash nominated Adam Strange
Green lantern nominated Green Arrow
Batman nominated Hawkman

And Uncle Tom, who likely read that comic brand-new, gets it right! (A year later the story in Mystery In Space #75 was published, set chronologically between JLofA #'s 3 and 4; it explained how the Flash could have nominated Adam Strange, when the world at large was unaware of his career as the Champion of Rann!)

Yeah, based on that hint, I would have to go with Adam Strange (ruled him out since he had commute issues). Then it would be him and Hawkman or Atom. Just to be different from Tom, I'll say Atom.

Yep, I used to really get my 12 cents worth back then!
Funny thing is, even as a 9 year old I thought Snapper Carr was a ######!

So how long do I have to come up with a new question? The natives got restless on the Marvel thread

It's mostly JTR who gets impatient, and that only when he's been cheeking his meds. Take your time.

How about we stay with the same team, same time period.

In the JLA's origin story, there are a number of menaces (of course) and the final one, a Diamond Creature, is defeated by Superman in a unique way.
How did the man of steel (in artwork rather like the Hypertime Superman!) overcome this threat?