Why does Gatsby start to laugh? In chapter 5?

His bedroom was the simplest room of all—except where the dresser was garnished with a toilet set of pure dull gold. Daisy took the brush with delight and smoothed her hair, whereupon Gatsby sat down and shaded his eyes and began to laugh.

"It's the funniest thing, old sport," he said hilariously. "I can't—when I try to—"

He had passed visibly through two states and was entering upon a third. After his embarrassment and his unreasoning joy he was consumed with wonder at her presence. He had been full of the idea so long, dreamed it right through to the end, waited with his teeth set, so to speak, at an inconceivable pitch of intensity. Now, in the reaction, he was running down like an overwound clock.

Recovering himself in a minute he opened for us two hulking patent cabinets which held his massed suits and dressing-gowns and ties, and his shirts, piled like bricks in stacks a dozen high.

Explanation:

https://www.sparknotes.com/lit/gatsby/full-text/chapter-5/

Hope this helps.

he will find out what went wrong or happened and how.

c. to understand which information will best persuade your readers. (apex) correct answer.