Explanation:

- The passage is about the origins of the name Elephant Island, associated with its appearance and animal sightings.

- In blank (1), it likely refers to the visual analogy of the island’s shape.

- Blank (2) requires a word to explain who first sighted the elephant seals.

- Option 1: "through" implies a medium or process, not fitting in this context.

- Option 2: "from" indicates origin, but not appropriate for describing an observer.

- Option 3: "among" typically denotes inclusion within a group, not relevant here.

- Option 4: "by" correctly denotes the agent performing the action, Captain George Powell.

- Blanks (3) and (4) are historical context about the island's discoveries.

- Blank (5) suggests a name given by the discoverers.

The correct answer is Option 4: by.