How does GA know about Clark's powers when Clark actually showed him so little?

[Iolanthe]

What I want to know: How does Oliver (aka Green Arrow) know that Clark has superpowers? All I saw Clark do was catch an arrow in mid-flight, and stand up to Oliver's punches. Did Oliver see him use heat vision, or superspeed? It's like GA knows that Clark is an alien already, but that's never said or explicated in the episode.

Example is in the later episode where Oliver is working out and Clark comes in; Oliver says, "It's exercise, Clark; something we mere mortals have to do." That implies he knows Clark isn't mortal. But when was this said/shown?

[LimeArrow]

No one can catch an arrow in mid-air. And how the hell did he dodge the second arrow when he's 3 feet away.

[jimmyolsenblues]

ollie could know more with his satellites.
They never explained how his spy satellites worked and no one's elses worked.
plus clark did catch his punch and toss him across the floor.

[SheaMan]

Seeing as Green Arrow has perfected the human body so well he can time an arrow flight to intersect with a bullet... I imagine he is fully aware of the limits of human potential.

Nobody can throw a human across the room. That alone was enough to remove any doubts that Clark has powers. Catching an arrow at 3 feet? Thats just icing. Then there is the "wierd shower of sparks" that Clark took credit for.

More than enough to come to the unqualified conclusion that Clark has mega-powers of some kind.