Filling Blanks: Understanding Adverb Usage in Context

The question asks us to select the most appropriate word to fill in the blank in the following sentence:

"But ________ at first such battles were rare, because human beings were few."

We need an adverb that logically connects the idea of battles being rare with the reason given (few humans). Let's analyze the options:

Option Analysis

• 1. closely: This adverb means 'near' or 'attentively'. It doesn't make sense to say battles were 'closely' rare. The word doesn't fit the context of explaining *why* something was rare.
• 2. accidentally: This adverb means 'by chance'. While battles can happen accidentally, using it here ("But accidentally at first such battles were rare") doesn't logically follow the reason provided. It doesn't explain the rarity itself based on population.
• 3. vivaciously: This adverb means 'lively' or 'energetically'. It's completely unrelated to the context of battles being rare or the reason for it. It doesn't fit grammatically or semantically.
• 4. probably: This adverb means 'likely' or 'most likely'. The sentence "But probably at first such battles were rare, because human beings were few" makes logical sense. It suggests that it is likely or reasonable to assume that battles were rare initially due to the small human population. This option connects the cause (few humans) to the effect (rare battles) smoothly.
• 5. (Empty Option): This is not a valid word choice.

Conclusion

The adverb 'probably' fits best because it introduces a likely explanation for the rarity of battles, directly linking it to the subsequent reason about the small number of humans.