The first premise says the lagoon is "home to many frogs," not that all known frogs on the island are in the lagoon. There could be plenty of frogs outside the lagoon too. Without establishing that all known frogs are in the lagoon, the argument doesn't match feature 1.

"The frogs are eaten only by the owls" tells us that nothing else eats the frogs. But that's not the same as saying the owls eat nothing but frogs. Compare this to the stimulus: we're told Ashley collects only tanzanite, meaning tanzanite is the only thing she collects. (B) would need to say the owls eat only frogs, but instead it says frogs are eaten only by the owls. The "only" is attached to the wrong part. Since the owls might eat plenty of other animals besides frogs, including ones outside the lagoon, the conclusion doesn't follow.

(C) is the trickiest wrong answer because it sounds like the stimulus, but the first premise points in the wrong direction. "Frogs are the only animals known to live in the lagoon" tells us what's inside the lagoon (just frogs, no other animals). But we need to know where the frogs are, not what else is in the lagoon. Compare: the stimulus says all known tanzanite is in Tanzania. It doesn't say tanzanite is the only mineral in Tanzania. Those are very different claims.

To see why this matters, think about what the first sentence of (C) allows. Maybe frogs live all over Scrag Island — on the beach, in the forest, in the lagoon. (C) tells us that frogs are the sole animal in the lagoon, not that the lagoon is the sole home of the frogs. So when the owls eat frogs from the island, those frogs could easily come from outside the lagoon. The conclusion that the owls are unlikely to eat something from outside the lagoon doesn't follow.

Every piece of (D) lines up with the stimulus.

Stimulus

All known tanzanite is in Tanzania.

Ashley collects only tanzanite.

Ashley is unlikely to collect a stone not from Tanzania.

(D)

The only frogs discovered on the island live in the lagoon. ✓

Owls eat only frogs on the island. ✓

Owls will probably never eat an animal from outside the lagoon. ✓

The first premise confines (known) frogs to the lagoon, just like (known) tanzanite is confined to Tanzania. The second premise establishes that owls eat only frogs, just like Ashley collects only tanzanite. And the conclusion uses cautious language ("probably never") to say the owls are unlikely to eat something from outside the lagoon, just like Ashley is unlikely to collect a stone not from Tanzania.

(E) is close but too strong in two places. First, it states that "each frog on Scrag Island lives in the lagoon" as a definitive fact, not a claim about what's been discovered so far. Compare this to the stimulus's "all known deposits." Second, the conclusion says "no owl will eat anything that lives outside the lagoon," which is absolute rather than probabilistic. The stimulus carefully hedges with "unlikely." (E) drops the hedging entirely, making it a deductively certain argument rather than a probabilistic one.