Explanation:

- The passage discusses the diversity of spider habitats.

- Option 1: widely

- "Widely" is an adverb, which fits as it describes how spider habitats vary.

- Option 2: widest

- "Widest" is the superlative form of "wide." It's an adjective, which doesn't fit well here since the passage needs an adverb.

- Option 3: wide

- "Wide" is an adjective. It doesn't work because an adverb is necessary to modify the verb "vary."

- Option 4: wider

- "Wider" is the comparative form of "wide" and is an adjective, not fitting in the context.