He fixed his gaze upon a white sunshade that was advancing at snail’s pace from the beach. he could see it plainly between the gaunt trunks of the water-oaks and across the stretch of yellow camomile. which phrase from the excerpt gives the best evidence that “gaunt” means “thin”? “advancing at snail’s pace” “he could see it plainly” “across the stretch of yellow camomile” “trunks of the water-oaks”

The phrase from the excerpt that gives the best evidence that "gaunt" means "thin" is "He could see it plainly". Because he could see clearly and evidently  the sunshade advancing from the beach advancing at snail's pace, between and across the stretch, they all give an idea of thinness, but still he can see it clearly.

He could see it plainly.

Explanation:

breathe, think and analyze the situation, pull them aside and talk to them about it