(1) The Cambrian explosion was a period of rapid evolutionary change around 541 million years ago. (2) During this time, most major animal phyla appeared in the fossil record. (3) The exact causes of this biological diversification are still debated by scientists. (4) Some theories point to environmental changes, such as an increase in atmospheric oxygen, while others emphasize the evolution of new genetic toolkits.
How does sentence (4) relate to sentence (3)?
- It contradicts the claim made in sentence (3).
- It repeats the information from sentence (3) using different words.
- It states the accepted conclusion to the debate mentioned in sentence (3).
- It provides specific examples of the scientific debate mentioned in sentence (3). (correct answer)
Explanation: When you encounter questions about how sentences relate to each other, you're being tested on your ability to identify specific organizational patterns in writing. Look for signal words and examine what type of information each sentence contains. Sentence (3) states that "the exact causes of this biological diversification are still debated by scientists." This establishes that there's an ongoing scientific discussion with no settled conclusion. Sentence (4) then says "Some theories point to environmental changes... while others emphasize..." This structure gives you concrete examples of what that debate looks like—it shows you the different sides scientists are taking. Answer choice (D) is correct because sentence (4) illustrates the debate mentioned in sentence (3) by presenting specific competing theories (environmental changes versus genetic toolkits). Let's examine why the other choices miss the mark. Choice (A) is wrong because sentence (4) doesn't contradict sentence (3)—it supports the idea that there's debate by showing different viewpoints. Choice (B) is incorrect because sentence (4) doesn't repeat the same information; it moves from the general statement about debate to specific examples of that debate. Choice (C) is wrong because sentence (4) presents multiple competing theories rather than stating an accepted conclusion—the phrase "while others emphasize" indicates ongoing disagreement, not resolution. Watch for transition patterns like "some... while others" or "on one hand... on the other hand." These phrases typically signal that the author is providing examples of different perspectives rather than reaching conclusions.